diff --git a/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight.html b/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight.html
index 54294a1205..814a7601b0 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight.html
@@ -37,5 +37,6 @@ limitations under the License.
     </div>
   </template>
   <script src="gr-annotation.js"></script>
+  <script src="gr-range-normalizer.js"></script>
   <script src="gr-diff-highlight.js"></script>
 </dom-module>
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight.js b/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight.js
index 62e58ad90a..9d7dc2ff2a 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight.js
@@ -94,40 +94,12 @@
       }
     },
 
-    _getContentTextParent: function(target) {
-      var element = target;
-      if (element.nodeName === '#text') {
-        element = element.parentElement;
-      }
-      while (!element.classList.contains('contentText')) {
-        if (element.parentElement === null) {
-          return target;
-        }
-        element = element.parentElement;
-      }
-      return element;
-    },
-
-    /**
-     * Remap DOM range to whole lines of a diff if necessary. If the start or
-     * end containers are DOM elements that are singular pieces of syntax
-     * highlighting, the containers are remapped to the .contentText divs that
-     * contain the entire line of code.
-     *
-     * @param  {Object} range - the standard DOM selector range.
-     * @return {Object} A modified version of the range that correctly accounts
-     *     for syntax highlighting.
-     */
     _normalizeRange: function(range) {
-      var startContainer = this._getContentTextParent(range.startContainer);
-      var startOffset = range.startOffset + this._getTextOffset(startContainer,
-          range.startContainer);
-      var endContainer = this._getContentTextParent(range.endContainer);
-      var endOffset = range.endOffset + this._getTextOffset(endContainer,
-          range.endContainer);
+      range = GrRangeNormalizer.normalize(range);
       return {
-        start: this._normalizeSelectionSide(startContainer, startOffset),
-        end: this._normalizeSelectionSide(endContainer, endOffset),
+        start: this._normalizeSelectionSide(range.startContainer,
+            range.startOffset),
+        end: this._normalizeSelectionSide(range.endContainer, range.endOffset),
       };
     },
 
@@ -306,36 +278,5 @@
         return GrAnnotation.getLength(node);
       }
     },
-
-    /**
-     * Gets the character offset of the child within the parent.
-     * Performs a synchronous in-order traversal from top to bottom of the node
-     * element, counting the length of the syntax until child is found.
-     *
-     * @param {!Element} The root DOM element to be searched through.
-     * @param {!Element} The child element being searched for.
-     * @return {number}
-     */
-    _getTextOffset: function(node, child) {
-      var count = 0;
-      var stack = [node];
-      while (stack.length) {
-        var n = stack.pop();
-        if (n === child) {
-          break;
-        }
-        if (n.childNodes && n.childNodes.length !== 0) {
-          var arr = [];
-          for (var i = 0; i < n.childNodes.length; i++) {
-            arr.push(n.childNodes[i]);
-          }
-          arr.reverse();
-          stack = stack.concat(arr);
-        } else {
-          count += this._getLength(n);
-        }
-      }
-      return count;
-    },
   });
 })();
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight_test.html b/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight_test.html
index 2612f9a93d..2f1ded94af 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight_test.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-diff-highlight_test.html
@@ -498,14 +498,14 @@ limitations under the License.
         assert.notDeepEqual(spyCall.returnValue, range);
       });
 
-      test('_getTextOffset computes text offset', function() {
+      test('GrRangeNormalizer._getTextOffset computes text offset', function() {
         var content = stubContent(140, 'left');
         var child = content.lastChild.lastChild;
-        var result = element._getTextOffset(content, child);
+        var result = GrRangeNormalizer._getTextOffset(content, child);
         assert.equal(result, 73);
         content = stubContent(146, 'right');
         child = content.lastChild;
-        result = element._getTextOffset(content, child);
+        result = GrRangeNormalizer._getTextOffset(content, child);
         assert.equal(result, 0);
       });
       // TODO (viktard): Selection starts in line number.
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-range-normalizer.js b/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-range-normalizer.js
new file mode 100644
index 0000000000..8685d7d57e
--- /dev/null
+++ b/polygerrit-ui/app/elements/diff/gr-diff-highlight/gr-range-normalizer.js
@@ -0,0 +1,106 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the 'License');
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an 'AS IS' BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+(function(window) {
+  'use strict';
+
+  // Prevent redefinition.
+  if (window.GrRangeNormalizer) { return; }
+
+  // Astral code point as per https://mathiasbynens.be/notes/javascript-unicode
+  var REGEX_ASTRAL_SYMBOL = /[\uD800-\uDBFF][\uDC00-\uDFFF]/;
+
+  var GrRangeNormalizer = {
+    /**
+     * Remap DOM range to whole lines of a diff if necessary. If the start or
+     * end containers are DOM elements that are singular pieces of syntax
+     * highlighting, the containers are remapped to the .contentText divs that
+     * contain the entire line of code.
+     *
+     * @param {Object} range - the standard DOM selector range.
+     * @return {Object} A modified version of the range that correctly accounts
+     *     for syntax highlighting.
+     */
+    normalize: function(range) {
+      var startContainer = this._getContentTextParent(range.startContainer);
+      var startOffset = range.startOffset + this._getTextOffset(startContainer,
+          range.startContainer);
+      var endContainer = this._getContentTextParent(range.endContainer);
+      var endOffset = range.endOffset + this._getTextOffset(endContainer,
+          range.endContainer);
+      return {
+        startContainer: startContainer,
+        startOffset: startOffset,
+        endContainer: endContainer,
+        endOffset: endOffset,
+      };
+    },
+
+    _getContentTextParent: function(target) {
+      var element = target;
+      if (element.nodeName === '#text') {
+        element = element.parentElement;
+      }
+      while (!element.classList.contains('contentText')) {
+        if (element.parentElement === null) {
+          return target;
+        }
+        element = element.parentElement;
+      }
+      return element;
+    },
+
+    /**
+     * Gets the character offset of the child within the parent.
+     * Performs a synchronous in-order traversal from top to bottom of the node
+     * element, counting the length of the syntax until child is found.
+     *
+     * @param {!Element} The root DOM element to be searched through.
+     * @param {!Element} The child element being searched for.
+     * @return {number}
+     */
+    _getTextOffset: function(node, child) {
+      var count = 0;
+      var stack = [node];
+      while (stack.length) {
+        var n = stack.pop();
+        if (n === child) {
+          break;
+        }
+        if (n.childNodes && n.childNodes.length !== 0) {
+          var arr = [];
+          for (var i = 0; i < n.childNodes.length; i++) {
+            arr.push(n.childNodes[i]);
+          }
+          arr.reverse();
+          stack = stack.concat(arr);
+        } else {
+          count += this._getLength(n);
+        }
+      }
+      return count;
+    },
+
+    /**
+     * The DOM API textContent.length calculation is broken when the text
+     * contains Unicode. See https://mathiasbynens.be/notes/javascript-unicode .
+     * @param {Text} A text node.
+     * @return {Number} The length of the text.
+     */
+    _getLength: function(node) {
+      return node.textContent.replace(REGEX_ASTRAL_SYMBOL, '_').length;
+    },
+  };
+
+  window.GrRangeNormalizer = GrRangeNormalizer;
+})(window);
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.html b/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.html
index 3c24291b0d..6a02a2dd00 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.html
@@ -43,5 +43,6 @@ limitations under the License.
       <content></content>
     </div>
   </template>
+  <script src="../gr-diff-highlight/gr-range-normalizer.js"></script>
   <script src="gr-diff-selection.js"></script>
 </dom-module>
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.js b/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.js
index 35da901974..99c049b1fd 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection.js
@@ -83,7 +83,7 @@
       if (sel.rangeCount != 1) {
         return; // No multi-select support yet.
       }
-      var range = sel.getRangeAt(0);
+      var range = GrRangeNormalizer.normalize(sel.getRangeAt(0));
       var startLineEl = this.diffBuilder.getLineElByChild(range.startContainer);
       var endLineEl = this.diffBuilder.getLineElByChild(range.endContainer);
       var startLineNum = parseInt(startLineEl.getAttribute('data-value'), 10);
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection_test.html b/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection_test.html
index cdc7483857..1ac800d605 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection_test.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-selection/gr-diff-selection_test.html
@@ -157,12 +157,17 @@ limitations under the License.
     });
 
     test('copies content correctly', function() {
-      element.classList.add('selected-left');
-      element.classList.remove('selected-right');
       // Fetch the line number.
       element._cachedDiffBuilder.getLineElByChild = function(child) {
-        return child.parentElement.parentElement.previousElementSibling;
+        while (!child.classList.contains('content') && child.parentElement) {
+          child = child.parentElement;
+        }
+        return child.previousElementSibling;
       };
+
+      element.classList.add('selected-left');
+      element.classList.remove('selected-right');
+
       var selection = window.getSelection();
       var range = document.createRange();
       range.setStart(element.querySelector('div.contentText').firstChild, 3);