Add plugin placeholder and policy support (issue #1708)

- Default plugin loading policy can be specified using the new
  `--plugin-policy=[allow|block|detect]` command-line flag.
- Move CefRequestHandler::OnBeforePluginLoad to
  CefRequestContextHandler and add a new policy argument that
  supports different actions (allow, block, detect, disable) on a
  per-plugin-instance basis.
- Add CefContextMenuHandler::RunContextMenu for providing a custom
  context menu implementation.
- Add CefResourceBundleHandler::GetDataResourceForScale for
  returning scaled resources (issue #1272).
- Add CefResourceBundle for retrieving resources from the resource
  bundle (*.pak) files loaded by CEF during startup or via the
  CefResourceBundleHandler.
- Linux: Fix Debug build IO access warning with CefGetMimeType.
- cef_unittests: Move the refcounting implementation from TestHandler
  to subclasses in order to support interface inheritance from
  subclasses.

libcef/renderer/plugins/plugin_preroller.cc

@@ -0,0 +1,91 @@
+// Copyright 2015 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/renderer/plugins/plugin_preroller.h"
+
+#include "libcef/renderer/plugins/cef_plugin_placeholder.h"
+
+#include "base/base64.h"
+#include "chrome/grit/generated_resources.h"
+#include "third_party/WebKit/public/platform/WebRect.h"
+#include "third_party/WebKit/public/web/WebElement.h"
+#include "third_party/WebKit/public/web/WebPlugin.h"
+#include "third_party/WebKit/public/web/WebPluginContainer.h"
+#include "ui/gfx/codec/png_codec.h"
+
+CefPluginPreroller::CefPluginPreroller(
+    content::RenderFrame* render_frame,
+    blink::WebLocalFrame* frame,
+    const blink::WebPluginParams& params,
+    const content::WebPluginInfo& info,
+    const std::string& identifier,
+    const base::string16& name,
+    const base::string16& message,
+    content::PluginInstanceThrottler* throttler)
+    : RenderFrameObserver(render_frame),
+      frame_(frame),
+      params_(params),
+      info_(info),
+      identifier_(identifier),
+      name_(name),
+      message_(message),
+      throttler_(throttler) {
+  DCHECK(throttler);
+  throttler_->AddObserver(this);
+}
+
+CefPluginPreroller::~CefPluginPreroller() {
+  if (throttler_)
+    throttler_->RemoveObserver(this);
+}
+
+void CefPluginPreroller::OnKeyframeExtracted(const SkBitmap* bitmap) {
+  std::vector<unsigned char> png_data;
+  if (!gfx::PNGCodec::EncodeBGRASkBitmap(*bitmap, false, &png_data)) {
+    DLOG(ERROR) << "Provided keyframe could not be encoded as PNG.";
+    return;
+  }
+
+  base::StringPiece png_as_string(reinterpret_cast<char*>(&png_data[0]),
+                                  png_data.size());
+
+  std::string data_url_header = "data:image/png;base64,";
+  std::string data_url_body;
+  base::Base64Encode(png_as_string, &data_url_body);
+  keyframe_data_url_ = GURL(data_url_header + data_url_body);
+}
+
+void CefPluginPreroller::OnThrottleStateChange() {
+  if (!throttler_->IsThrottled())
+    return;
+
+  PlaceholderPosterInfo poster_info;
+  poster_info.poster_attribute = keyframe_data_url_.spec();
+  poster_info.custom_poster_size = throttler_->GetSize();
+
+  CefPluginPlaceholder* placeholder =
+      CefPluginPlaceholder::CreateBlockedPlugin(
+          render_frame(), frame_, params_, info_, identifier_, name_,
+          IDR_PLUGIN_POSTER_HTML, message_, poster_info);
+  placeholder->SetPremadePlugin(throttler_);
+  placeholder->set_power_saver_enabled(true);
+  placeholder->AllowLoading();
+
+  blink::WebPluginContainer* container =
+      throttler_->GetWebPlugin()->container();
+  container->setPlugin(placeholder->plugin());
+
+  bool success = placeholder->plugin()->initialize(container);
+  DCHECK(success);
+
+  container->invalidate();
+  container->reportGeometry();
+
+  delete this;
+}
+
+void CefPluginPreroller::OnThrottlerDestroyed() {
+  throttler_ = nullptr;
+  delete this;
+}