chromeos: Enable RenderTextHarfBuzz.

ui/gfx/render_text.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/render_text.h"
 
 #include <algorithm>
 #include <climits>
 
 #include "base/command_line.h"
@@ skipping 378 matching lines @@
 
 }  // namespace internal
 
 RenderText::~RenderText() {
 }
 
 RenderText* RenderText::CreateInstance() {
 #if defined(OS_MACOSX) && defined(TOOLKIT_VIEWS)
   // Use the more complete HarfBuzz implementation for Views controls on Mac.
   return new RenderTextHarfBuzz;
+#endif
+
+#if defined(OS_LINUX)

[msw, 2014/10/07 18:29:01]

nit: elif?

[Daniel Erat, 2014/10/08 02:03:43]

sure, done

+  // RenderTextPango has severe performance issues (http://crbug.com/376077), so
+  // default to RenderTextHarfBuzz on Linux (and Chrome OS).
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableHarfBuzzRenderText)) {
+    return new RenderTextHarfBuzz;
+  }
 #else
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnableHarfBuzzRenderText)) {
     return new RenderTextHarfBuzz;
   }
+#endif
   return CreateNativeInstance();

[msw, 2014/10/07 18:29:01]

nit q: will this trigger unreachable code warnings on Mac Views builds?

[Daniel Erat, 2014/10/08 02:03:43]

good point. i think that nested ifdefs are pretty hard to read, so i'm hopeful
that this works, but i'll change it if it doesn't.

-#endif
 }
 
 void RenderText::SetText(const base::string16& text) {
   DCHECK(!composition_range_.IsValid());
   if (text_ == text)
     return;
   text_ = text;
 
   // Adjust ranged styles and colors to accommodate a new text length.
   // Clear style ranges as they might break new text graphemes and apply
@@ skipping 962 matching lines @@
   SetDisplayOffset(display_offset_.x() + delta_x);
 }
 
 void RenderText::DrawSelection(Canvas* canvas) {
   const std::vector<Rect> sel = GetSubstringBounds(selection());
   for (std::vector<Rect>::const_iterator i = sel.begin(); i < sel.end(); ++i)
     canvas->FillRect(*i, selection_background_focused_color_);
 }
 
 }  // namespace gfx