Fix issue with broken links in HyperlinkTextView.

If a link in a HyperlinkTextView does not begin at the start of the text
then a click that looks like a potential text selection will fail to
activate the link.

BUG=626021

Review-Url: https://codereview.chromium.org/2440913003
Cr-Commit-Position: refs/heads/master@{#427111}

ui/base/cocoa/controls/hyperlink_text_view.mm

@@ -54,8 +54,12 @@ const float kTextBaselineShift = -1.0;
 
 - (NSRange)selectionRangeForProposedRange:(NSRange)proposedSelRange
                               granularity:(NSSelectionGranularity)granularity {
-  // Do not allow selections.
-  return NSMakeRange(0, 0);
+  // Return a range of length 0 to prevent text selection. Note that the start
+  // of the range (the first argument) is treated as the position of the
+  // subsequent click so it must not be 0. If it is, links that begin at a
+  // non-zero position in the text will not function correctly when they are
+  // clicked in such a way as to look like a possible text selection.
+  return NSMakeRange(proposedSelRange.location, 0);
 }
 
 // Convince NSTextView to not show an I-Beam cursor when the cursor is over the

ui/base/cocoa/controls/hyperlink_text_view_unittest.mm

@@ -58,6 +58,20 @@ class HyperlinkTextViewTest : public ui::CocoaTest {
 
 TEST_VIEW(HyperlinkTextViewTest, view_);
 
+TEST_F(HyperlinkTextViewTest, TestSelectionRange) {
+  NSRange actualRange;
+
+  // The length of the selection range should be 0.
+  actualRange = [view_ selectionRangeForProposedRange:NSMakeRange(0, 20)
+                                          granularity:NSSelectByCharacter];
+  EXPECT_TRUE(NSEqualRanges(NSMakeRange(0, 0), actualRange));
+
+  // While the location should always match the location of the proposed range.
+  actualRange = [view_ selectionRangeForProposedRange:NSMakeRange(50, 100)
+                                          granularity:NSSelectByCharacter];
+  EXPECT_TRUE(NSEqualRanges(NSMakeRange(50, 0), actualRange));
+}
+
 TEST_F(HyperlinkTextViewTest, TestViewConfiguration) {
   EXPECT_FALSE([view_ isEditable]);
   EXPECT_FALSE([view_ drawsBackground]);