Make backspace not go back while IME is active.

chrome/browser/renderer_host/render_widget_host_view_mac.mm

 // Copyright (c) 2006-2008 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 "chrome/browser/renderer_host/render_widget_host_view_mac.h"
 
 #include "base/histogram.h"
 #include "base/scoped_nsobject.h"
 #include "base/string_util.h"
 #include "base/sys_string_conversions.h"
@@ skipping 570 matching lines @@
   NativeWebKeyboardEvent event(theEvent);
 
   // Save the modifier keys so the insertText method can use it when it sends
   // a Char event, which is dispatched as an onkeypress() event of JavaScript.
   renderWidgetHostView_->im_modifiers_ = event.modifiers;
 
   // To emulate Windows, over-write |event.windowsKeyCode| to VK_PROCESSKEY
   // while an input method is composing a text.
   // Gmail checks this code in its onkeydown handler to stop auto-completing
   // e-mail addresses while composing a CJK text.
-  if ([theEvent type] == NSKeyDown && renderWidgetHostView_->im_composing_)
-    event.windowsKeyCode = 0xE5;
+  if ([theEvent type] == NSKeyDown && renderWidgetHostView_->im_composing_) {
+    event.windowsKeyCode = 0xE5;  // VKEY_PROCESSKEY
+    event.setKeyIdentifierFromWindowsKeyCode();
+    event.skip_in_browser = true;
+  }
 
   // Dispatch this keyboard event to the renderer.
   if (renderWidgetHostView_->render_widget_host_) {
     RenderWidgetHost* widgetHost = renderWidgetHostView_->render_widget_host_;
     // Look up shortcut, if any, for this key combination.
     EditCommands editCommands;
     [EditCommandMatcher matchEditCommands:&editCommands forEvent:theEvent];
     if (!editCommands.empty())
       widgetHost->ForwardEditCommandsForNextKeyEvent(editCommands);
     widgetHost->ForwardKeyboardEvent(event);
@@ skipping 661 matching lines @@
     renderWidgetHostView_->render_widget_host_->ForwardKeyboardEvent(event);
   } else {
     renderWidgetHostView_->render_widget_host_->ImeConfirmComposition(
         UTF8ToUTF16([im_text UTF8String]));
   }
   renderWidgetHostView_->im_composing_ = false;
 }
 
 @end