Reduce texture uploads during scrollbar invalidations.

cc/caching_bitmap_canvas_layer_texture_updater.h

Index: cc/caching_bitmap_canvas_layer_texture_updater.h
diff --git a/cc/caching_bitmap_canvas_layer_texture_updater.h b/cc/caching_bitmap_canvas_layer_texture_updater.h
new file mode 100644
index 0000000000000000000000000000000000000000..60b8a03913a49afa36f19f9071fc8e675ccdbb81
--- /dev/null
+++ b/cc/caching_bitmap_canvas_layer_texture_updater.h
@@ -0,0 +1,42 @@
+// Copyright 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.
+
+#ifndef CachingBitmapCanvasLayerTextureUpdater_h

[enne (OOO), 2012/10/02 21:07:18]

If this is intended to be Chromium style, this is wrong.

[wjmaclean, 2012/10/02 21:43:46]

Done.

+#define CachingBitmapCanvasLayerTextureUpdater_h
+
+#if USE(ACCELERATED_COMPOSITING)

[jamesr, 2012/10/02 20:57:54]

don't do this

[wjmaclean, 2012/10/02 21:43:46]

Done.

+
+#include "BitmapCanvasLayerTextureUpdater.h"
+
+namespace cc {
+
+class CachingBitmapCanvasLayerTextureUpdater
+    : public BitmapCanvasLayerTextureUpdater {
+public:
+static PassRefPtr<CachingBitmapCanvasLayerTextureUpdater> Create(
+    PassOwnPtr<LayerPainterChromium>);
+
+virtual void prepareToUpdate(const IntRect& content_rect,

[jamesr, 2012/10/02 20:57:54]

what style is this intended to be? In WebKit style, this should be 4-space
indented. In chromium style, this should be 2-space indented and the
public/private declarations should have a 1-space indent

[wjmaclean, 2012/10/02 21:43:46]

It's meant to be Chromium-style, but I've been absent from that for a while and
so I'm rusty on it ... will fix these (and any others) ...

Done.

+                             const IntSize& tile_size,
+                             float contents_width_scale,
+                             float contents_height_scale,
+                             IntRect& resulting_opaque_rect,
+                             CCRenderingStats&) OVERRIDE;

[jamesr, 2012/10/02 20:57:54]

you need base/compiler_specific.h to use OVERRIDE in chromium style code

[wjmaclean, 2012/10/02 21:43:46]

Done.

+virtual void updateTextureRect(CCResourceProvider*,

[jamesr, 2012/10/02 20:57:54]

blank line between functions please

[wjmaclean, 2012/10/02 21:43:46]

Done.

+                               CCPrioritizedTexture*,
+                               const IntRect& source_rect,
+                               const IntSize& dest_offset) OVERRIDE;
+
+private:
+  CachingBitmapCanvasLayerTextureUpdater(
+    PassOwnPtr<LayerPainterChromium> painter);
+
+  bool texture_ueeds_upload_;

[jamesr, 2012/10/02 20:57:54]

typo 'ueeds'

[wjmaclean, 2012/10/02 21:43:46]

Done.

+  SkBitmap cached_bitmap_;
+};
+
+} // namespace cc

[enne (OOO), 2012/10/02 21:07:18]

Two spaces between } and //

[wjmaclean, 2012/10/02 21:43:46]

Done.

+
+#endif // USE(ACCELERATED_COMPOSITING)
+#endif // CachingBitmapCanvasLayerTextureUpdater_h

[enne (OOO), 2012/10/02 21:07:18]

Two spaces between #endif and // too.

[wjmaclean, 2012/10/02 21:43:46]

Done.