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

libcef/browser/render_widget_host_view_osr_win.cc

@@ -0,0 +1,59 @@
+// Copyright (c) 2014 The Chromium Embedded Framework Authors.
+// Portions copyright (c) 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.
+
+#include "libcef/browser/render_widget_host_view_osr.h"
+#include "libcef/browser/browser_host_impl.h"
+
+namespace {
+
+class CefCompositorHostWin : public gfx::WindowImpl {
+ public:
+  CefCompositorHostWin() {
+    // Create a hidden 1x1 borderless window.
+    set_window_style(WS_POPUP | WS_SYSMENU);
+    Init(NULL, gfx::Rect(0, 0, 1, 1));
+  }
+
+  virtual ~CefCompositorHostWin() {
+    DestroyWindow(hwnd());
+  }
+
+ private:
+  CR_BEGIN_MSG_MAP_EX(CompositorHostWin)
+    CR_MSG_WM_PAINT(OnPaint)
+  CR_END_MSG_MAP()
+
+  void OnPaint(HDC dc) {
+    ValidateRect(hwnd(), NULL);
+  }
+
+  DISALLOW_COPY_AND_ASSIGN(CefCompositorHostWin);
+};
+
+}  // namespace
+
+void CefRenderWidgetHostViewOSR::SetParentNativeViewAccessible(
+    gfx::NativeViewAccessible accessible_parent) {
+}
+
+gfx::NativeViewId
+    CefRenderWidgetHostViewOSR::GetParentForWindowlessPlugin() const {
+  if (browser_impl_.get()) {
+    return reinterpret_cast<gfx::NativeViewId>(
+        browser_impl_->GetWindowHandle());
+  }
+  return NULL;
+}
+
+void CefRenderWidgetHostViewOSR::PlatformCreateCompositorWidget() {
+  DCHECK(!window_);
+  window_.reset(new CefCompositorHostWin());
+  compositor_widget_ = window_->hwnd();
+}
+
+void CefRenderWidgetHostViewOSR::PlatformDestroyCompositorWidget() {
+  window_.reset(NULL);
+  compositor_widget_ = gfx::kNullAcceleratedWidget;
+}