Distinguish between error and timeout in intraline diff error message

When the intraline diff fails, the error message simply says that
there was a server error.  It could be that the reason for failure
is a timeout, but it's not possible to know this from the error
message.

Add a new error message that is displayed when the intraline diff
fails due to timeout.

Also update the documentation to mention that an error message is
displayed if the intraline diff times out.

Change-Id: I93410d853aadc7ed1f6e4324d0578c4bcbe4e195

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchConstants.java

@@ -36,6 +36,7 @@ public interface PatchConstants extends Constants {
   String patchHistoryTitle();
   String disabledOnLargeFiles();
   String intralineFailure();
+  String intralineTimeout();
   String illegalNumberOfColumns();
 
   String upToChange();

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchConstants.properties

@@ -18,6 +18,7 @@ patchHistoryTitle = Patch History
 patchSet = Patch Set
 disabledOnLargeFiles = Disabled on very large source files.
 intralineFailure = Intraline difference not available due to server error.
+intralineTimeout = Intraline difference not available due to timeout.
 illegalNumberOfColumns = The number of columns cannot be zero or negative
 
 upToChange = Up to change

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchScreen.java

@@ -120,6 +120,7 @@ public abstract class PatchScreen extends Screen implements
   private HandlerRegistration regNavigation;
   private HandlerRegistration regAction;
   private boolean intralineFailure;
+  private boolean intralineTimeout;
 
   /**
    * How this patch should be displayed in the patch screen.
@@ -468,6 +469,7 @@ public abstract class PatchScreen extends Screen implements
     }
 
     intralineFailure = isFirst && script.hasIntralineFailure();
+    intralineTimeout = isFirst && script.hasIntralineTimeout();
   }
 
   @Override
@@ -476,6 +478,9 @@ public abstract class PatchScreen extends Screen implements
     if (intralineFailure) {
       intralineFailure = false;
       new ErrorDialog(PatchUtil.C.intralineFailure()).show();
+    } else if (intralineTimeout) {
+      intralineTimeout = false;
+      new ErrorDialog(PatchUtil.C.intralineTimeout()).show();
     }
     if (topView != null && prefs.get().isRetainHeader()) {
       setTopView(topView);