Fix yet another ArrayIndexOutOfBounds during side-by-side view

We messed up the mapping when converting from side B line numbers
to side A line numbers, resulting in an EMPTY edit being placed
too early in a file when it fell between two INSERT edits.  This
had the effect of making Gerrit skip over an entire INSERT, which
then threw off the line numbering on the B side when creating the
side-by-side or unified view for certain files.

Signed-off-by: Shawn O. Pearce <sop@google.com>

src/main/java/com/google/gerrit/client/data/EditList.java

@@ -138,7 +138,7 @@ public class EditList {
     }
 
     public boolean isContextLine() {
-      return !isModifiedLine() || endIdx + 1 < curIdx;
+      return !isModifiedLine();
     }
 
     public boolean isDeletedA() {
@@ -154,8 +154,10 @@ public class EditList {
     }
 
     public boolean next() {
-      if (!in(curEdit) && ++curIdx < edits.size()) {
+      if (!in(curEdit)) {
-        curEdit = edits.get(curIdx);
+        if (curIdx < endIdx) {
+          curEdit = edits.get(++curIdx);
+        }
       }
       return aCur < aEnd || bCur < bEnd;
     }

src/main/java/com/google/gerrit/server/rpc/patch/PatchScriptBuilder.java

@@ -271,7 +271,7 @@ class PatchScriptBuilder {
           //
           return a;
         }
-        return edits.get(i - i).getEndB() + (e.getBeginA() - a);
+        return e.getBeginB() - (e.getBeginA() - a);
       }
       if (e.getBeginA() <= a && a <= e.getEndA()) {
         return -1;
@@ -297,7 +297,7 @@ class PatchScriptBuilder {
           //
           return b;
         }
-        return edits.get(i - i).getEndA() + (e.getBeginB() - b);
+        return e.getBeginA() - (e.getBeginB() - b);
       }
       if (e.getBeginB() <= b && b <= e.getEndB()) {
         return -1;