Implement off-screen rendering support using delegated rendering (issue #1257).

This implementation supports both GPU compositing and software compositing (used when GPU is not supported or when passing `--disable-gpu --disable-gpu-compositing` command-line flags). GPU-accelerated features (WebGL and 3D CSS) that did not work with the previous off-screen rendering implementation do work with this implementation when GPU support is available.

Rendering now operates on a per-frame basis. The frame rate is configurable via CefBrowserSettings.windowless_frame_rate up to a maximum of 60fps (potentially limited by how fast the system can generate new frames). CEF generates a bitmap from the compositor backing and passes it to CefRenderHandler::OnPaint.

The previous CefRenderHandler/CefBrowserHost API for off-screen rendering has been restored mostly as-is with some minor changes:

- CefBrowserHost::Invalidate no longer accepts a CefRect region argument. Instead of invalidating a specific region it now triggers generation of a new frame.
- The |dirtyRects| argument to CefRenderHandler::OnPaint will now always be a single CefRect representing the whole view (frame) size. Previously, invalidated regions were listed separately.
- Linux: CefBrowserHost::SendKeyEvent now expects X11 event information instead of GTK event information. See cefclient for an example of converting GTK events to the necessary format.
- Sizes passed to the CefRenderHandler OnPaint and OnPopupSize methods are now already DPI scaled. Previously, the client had to perform DPI scaling.
- Includes drag&drop implementation from issue #1032.
- Includes unit test fixes from issue #1245.

git-svn-id: https://chromiumembedded.googlecode.com/svn/trunk@1751 5089003a-bbd8-11dd-ad1f-f1f9622dbc98

patch/patch.cfg

@@ -47,6 +47,11 @@ patches = [
     'name': 'gyp_331',
     'path': '../tools/gyp/pylib/',
   },
+  {
+    # Enable popups in offscreen rendering on OS X.
+    'name': 'webkit_popups',
+    'path': '../third_party/WebKit/',
+  },
   {
     # Fix export of UnderlayOpenGLHostingWindow for 64-bit OS X builds.
     # http://code.google.com/p/chromiumembedded/issues/detail?id=1051
@@ -74,9 +79,18 @@ patches = [
   {
     # Allow customization of the background color with Aura.
     # http://code.google.com/p/chromiumembedded/issues/detail?id=1161
-    'name': 'public_browser_1161',
+    #
+    # Allow specification of a custom WebContentsView.
+    # http://code.google.com/p/chromiumembedded/issues/detail?id=1257
+    'name': 'public_browser_1161_1257',
     'path': '../content/public/browser/',
   },
+  {
+    # Allow specification of a custom WebContentsView.
+    # http://code.google.com/p/chromiumembedded/issues/detail?id=1257
+    'name': 'browser_web_contents_1257',
+    'path': '../content/browser/web_contents/',
+  },
   {
     # Allow customization of the WebView background color.
     # http://code.google.com/p/chromiumembedded/issues/detail?id=1161