Combine ViewHostMsg_{Paint,Scroll}Rect into one IPC....

Combine ViewHostMsg_{Paint,Scroll}Rect into one IPC.

The combined IPC means that scrolling only requires one transport DIB instead
of two.  Previously, we'd use one in the ScrollRect IPC to pass up the pixels
for the exposed region, and then we'd use a second one in the PaintRect IPC to
pass up the pixels for the updated scroll bar rendering.  Now all paints are
done using a single transport DIB.

Optimize RenderWidgetHostViewWin::OnPaint to only paint the damaged regions.
This means calling GetUpdateRgn and GetRegionData to enumerate the list of
damage rects.  Then only those rects are copied from the backing store.

The same optimization is not done for Linux or Mac yet.

R=brettw
BUG=29591
TEST=none


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=34951

[brettw, 2009-12-17 04:41:13]

LGTM.

PS GetRegionData is a terrible API!

http://codereview.chromium.org/506013/diff/3026/3040
File chrome/browser/renderer_host/backing_store.h (right):

http://codereview.chromium.org/506013/diff/3026/3040#newcode101
chrome/browser/renderer_host/backing_store.h:101: // Scrolls the given rect in
the backing store, replacing the given region
This comment is out of date.

http://codereview.chromium.org/506013/diff/3026/3045
File chrome/browser/renderer_host/render_widget_host.cc (right):

http://codereview.chromium.org/506013/diff/3026/3045#newcode689
chrome/browser/renderer_host/render_widget_host.cc:689:
view_->DidScrollBackingStoreRect(params.scroll_rect, params.dx, params.dy);
Too long

http://codereview.chromium.org/506013/diff/3026/3041
File chrome/browser/renderer_host/render_widget_host_view_mac.mm (right):

http://codereview.chromium.org/506013/diff/3026/3041#newcode287
chrome/browser/renderer_host/render_widget_host_view_mac.mm:287: // As much as
we'd like to use -setNeedsDisplayInRect: here, we can't. We're
Your extra indentation made this too long.

http://codereview.chromium.org/506013/diff/3026/3050
File chrome/common/render_messages.h (right):

http://codereview.chromium.org/506013/diff/3026/3050#newcode206
chrome/common/render_messages.h:206: // The scroll offset.  Only one of these
can be non-zero.
It might be nice to also mention that they can both be zero to indicate no
scroll.