Optionally clear PlatformCanvas instances.

webkit/tools/test_shell/webwidget_host_win.cc

 // Copyright (c) 2011 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 "webkit/tools/test_shell/webwidget_host.h"
 
 #include "base/logging.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPopupMenu.h"
@@ skipping 116 matching lines @@
       case WM_SETFOCUS:
         host->SetFocus(true);
         break;
 
       case WM_KILLFOCUS:
         host->SetFocus(false);
         break;
     }
   }
 
-  return DefWindowProc(hwnd, message, wparam, lparam);;
+  return DefWindowProc(hwnd, message, wparam, lparam);
 }
 
 void WebWidgetHost::DidInvalidateRect(const gfx::Rect& damaged_rect) {
   DLOG_IF(WARNING, painting_) << "unexpected invalidation while painting";
 
   // If this invalidate overlaps with a pending scroll, then we have to
   // downgrade to invalidating the scroll rect.
   if (damaged_rect.Intersects(scroll_rect_)) {
     paint_rect_ = paint_rect_.Union(scroll_rect_);
     ResetScrollRect();
@@ skipping 86 matching lines @@
   RECT r;
   GetClientRect(view_, &r);
   gfx::Rect client_rect(r);
 
   // Allocate a canvas if necessary
   if (!canvas_.get()) {
     ResetScrollRect();
     paint_rect_ = client_rect;
     canvas_.reset(new skia::PlatformCanvas(
         paint_rect_.width(), paint_rect_.height(), true));
+    canvas_->drawARGB(0, 0, 0, 0);
   }
 
   webwidget_->animate(0.0);
 
   // This may result in more invalidation
   webwidget_->layout();
 
   // Scroll the canvas if necessary
   scroll_rect_ = client_rect.Intersect(scroll_rect_);
   if (!scroll_rect_.IsEmpty()) {
@@ skipping 119 matching lines @@
 void WebWidgetHost::PaintRect(const gfx::Rect& rect) {
 #ifndef NDEBUG
   DCHECK(!painting_);
 #endif
   DCHECK(canvas_.get());
 
   set_painting(true);
   webwidget_->paint(canvas_.get(), rect);
   set_painting(false);
 }