Remove RenderWidget::SetBackground, change IPC to pass a bool.

content/common/view_messages.h

 // 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.
 
 // IPC messages for page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include "base/memory/shared_memory.h"
 #include "base/process/process.h"
 #include "base/strings/string16.h"
@@ skipping 801 matching lines @@
 IPC_MESSAGE_ROUTED1(ViewMsg_DisableAutoResize,
                     gfx::Size /* new_size */)
 
 // Changes the text direction of the currently selected input field (if any).
 IPC_MESSAGE_ROUTED1(ViewMsg_SetTextDirection,
                     blink::WebTextDirection /* direction */)
 
 // Tells the renderer to clear the focused element (if any).
 IPC_MESSAGE_ROUTED0(ViewMsg_ClearFocusedElement)
 
-// Make the RenderView transparent and render it onto a custom background. The
-// background will be tiled in both directions if it is not large enough.
-IPC_MESSAGE_ROUTED1(ViewMsg_SetBackground,
-                    SkBitmap /* background */)
+// Make the RenderView background transparent or opaque.
+IPC_MESSAGE_ROUTED1(ViewMsg_SetBackgroundOpaque,
+                    bool /* opaque */)
 
 // Used to tell the renderer not to add scrollbars with height and
 // width below a threshold.
 IPC_MESSAGE_ROUTED1(ViewMsg_DisableScrollbarsForSmallWindows,
                     gfx::Size /* disable_scrollbar_size_limit */)
 
 // Activate/deactivate the RenderView (i.e., set its controls' tint
 // accordingly, etc.).
 IPC_MESSAGE_ROUTED1(ViewMsg_SetActive,
                     bool /* active */)
@@ skipping 941 matching lines @@
 // synchronously (see crbug.com/120597). This IPC message sends the character
 // bounds after every composition change to always have correct bound info.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_ImeCompositionRangeChanged,
                     gfx::Range /* composition range */,
                     std::vector<gfx::Rect> /* character bounds */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent ViewMsg, then ifdefs for platform specific ViewMsg, then platform
 // independent ViewHostMsg, then ifdefs for platform specific ViewHostMsg.