Avoid flashing when resizing plugins that use PaintManager. Copy the bitmap ...

webkit/glue/plugins/pepper_plugin_instance.cc

 // Copyright (c) 2010 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/glue/plugins/pepper_plugin_instance.h"
 
 #include "base/logging.h"
 #include "base/histogram.h"
 #if defined(OS_MACOSX)
 #include "base/mac_util.h"
@@ skipping 296 matching lines @@
     }
     return true;
   }
 
   scoped_refptr<DeviceContext2D> device_2d =
       Resource::GetAs<DeviceContext2D>(device_id);
 
   if (device_2d) {
     if (!device_2d->BindToInstance(this))
       return false;  // Can't bind to more than one instance.
+
+    if (device_context_2d_.get()) {
+      // Start the new image with the content of the old image until the plugin
+      // repaints.
+      const SkBitmap* old_backing_bitmap =
+          device_context_2d_->image_data()->GetMappedBitmap();
+      SkRect old_size = SkRect::MakeWH(
+          SkScalar(static_cast<float>(old_backing_bitmap->width())),
+          SkScalar(static_cast<float>(old_backing_bitmap->height())));
+
+      SkCanvas canvas(*device_2d->image_data()->GetMappedBitmap());
+      canvas.drawBitmap(*old_backing_bitmap, 0, 0);
+
+      // Fill in any extra space with white.
+      canvas.clipRect(old_size, SkRegion::kDifference_Op);
+      canvas.drawARGB(255, 255, 255, 255);
+    }
+
     device_context_2d_ = device_2d;
     // BindToInstance will have invalidated the plugin if necessary.
   }
 
   return true;
 }
 
 bool PluginInstance::SetCursor(PP_CursorType type) {
   cursor_.reset(new WebCursorInfo(static_cast<WebCursorInfo::Type>(type)));
   return true;
@@ skipping 472 matching lines @@
   bounds.size.width = dest_rect.width();
   bounds.size.height = dest_rect.height();
 
   CGContextDrawImage(canvas, bounds, image);
   CGContextRestoreGState(canvas);
 }
 #endif  // defined(OS_MACOSX)
 
 
 }  // namespace pepper