Plugin Power Saver: Implement srcset syntax for posters.

The objective of the patch is that the poster attribute for plugins can support high-dpi images via the img srcset syntax, i.e.

<param name="poster" value="poster1x.png 1x, poster2x.png 2x" />

BUG=457333

Review URL: https://codereview.chromium.org/981623003

Cr-Commit-Position: refs/heads/master@{#319689}

chrome/renderer/chrome_content_renderer_client.cc

@@ -318,17 +318,17 @@ void TrackPosterParamPresence(const blink::WebPluginParams& params,
     RecordPosterParamPresence(POSTER_PRESENCE_NO_PARAM_PPS_DISABLED);
 }
 
-GURL GetPluginInstancePosterImage(const blink::WebPluginParams& params,
-                                  const GURL& page_base_url) {
+std::string GetPluginInstancePosterAttribute(
+    const blink::WebPluginParams& params) {
   DCHECK_EQ(params.attributeNames.size(), params.attributeValues.size());
 
   for (size_t i = 0; i < params.attributeNames.size(); ++i) {
     if (params.attributeNames[i].utf8() == "poster" &&
         !params.attributeValues[i].isEmpty()) {
-      return page_base_url.Resolve(params.attributeValues[i].utf8());
+      return params.attributeValues[i].utf8();
     }
   }
-  return GURL();
+  return std::string();
 }
 #endif
 
@@ -796,10 +796,10 @@ WebPlugin* ChromeContentRendererClient::CreatePlugin(
     auto create_blocked_plugin =
         [&render_frame, &frame, &params, &info, &identifier, &group_name](
             int template_id, const base::string16& message) {
-      return ChromePluginPlaceholder::CreateBlockedPlugin(
-          render_frame, frame, params, info, identifier, group_name,
-          template_id, message, GURL());
-    };
+          return ChromePluginPlaceholder::CreateBlockedPlugin(
+              render_frame, frame, params, info, identifier, group_name,
+              template_id, message, std::string(), GURL());
+        };
     switch (status_value) {
       case ChromeViewHostMsg_GetPluginInfo_Status::kNotFound: {
         NOTREACHED();
@@ -878,11 +878,9 @@ WebPlugin* ChromeContentRendererClient::CreatePlugin(
         if (info.name == ASCIIToUTF16(content::kFlashPluginName))
           TrackPosterParamPresence(params, power_saver_enabled);
 
-        GURL poster_url;
-        if (power_saver_enabled) {
-          poster_url =
-              GetPluginInstancePosterImage(params, frame->document().url());
-        }
+        std::string poster_attribute;
+        if (power_saver_enabled)
+          poster_attribute = GetPluginInstancePosterAttribute(params);
 
         // Delay loading plugins if prerendering.
         // TODO(mmenke):  In the case of prerendering, feed into
@@ -891,13 +889,13 @@ WebPlugin* ChromeContentRendererClient::CreatePlugin(
         bool is_prerendering =
             prerender::PrerenderHelper::IsPrerendering(render_frame);
         if (blocked_for_background_tab || is_prerendering ||
-            poster_url.is_valid()) {
+            !poster_attribute.empty()) {
           placeholder = ChromePluginPlaceholder::CreateBlockedPlugin(
               render_frame, frame, params, info, identifier, group_name,
-              poster_url.is_valid() ? IDR_PLUGIN_POSTER_HTML
-                                    : IDR_BLOCKED_PLUGIN_HTML,
+              poster_attribute.empty() ? IDR_BLOCKED_PLUGIN_HTML
+                                       : IDR_PLUGIN_POSTER_HTML,
               l10n_util::GetStringFUTF16(IDS_PLUGIN_BLOCKED, group_name),
-              poster_url);
+              poster_attribute, frame->document().url());
           placeholder->set_blocked_for_background_tab(
               blocked_for_background_tab);
           placeholder->set_blocked_for_prerendering(is_prerendering);

chrome/renderer/plugins/chrome_plugin_placeholder.cc

@@ -153,14 +153,17 @@ ChromePluginPlaceholder* ChromePluginPlaceholder::CreateBlockedPlugin(
     const base::string16& name,
     int template_id,
     const base::string16& message,
-    const GURL& poster_url) {
+    const std::string& poster_attribute,
+    const GURL& base_url) {
   base::DictionaryValue values;
   values.SetString("message", message);
   values.SetString("name", name);
   values.SetString("hide", l10n_util::GetStringUTF8(IDS_PLUGIN_HIDE));
 
-  if (poster_url.is_valid())
-    values.SetString("background", "url('" + poster_url.spec() + "')");
+  if (!poster_attribute.empty()) {
+    values.SetString("poster", poster_attribute);
+    values.SetString("baseurl", base_url.spec());
+  }
 
   const base::StringPiece template_html(
       ResourceBundle::GetSharedInstance().GetRawDataResource(template_id));
@@ -174,7 +177,7 @@ ChromePluginPlaceholder* ChromePluginPlaceholder::CreateBlockedPlugin(
       render_frame, frame, params, html_data, name);
 
 #if defined(ENABLE_PLUGINS)
-  if (poster_url.is_valid())
+  if (!poster_attribute.empty())
     blocked_plugin->BlockForPowerSaverPoster();
 #endif
   blocked_plugin->SetPluginInfo(info);

chrome/renderer/plugins/chrome_plugin_placeholder.h

@@ -17,6 +17,8 @@ class ChromePluginPlaceholder : public plugins::LoadablePluginPlaceholder,
  public:
   static const char kPluginPlaceholderDataURL[];
 
+  // If |poster_attribute| contains relative paths, |base_url| must be
+  // non-empty. This is so the placeholder can resolve the relative paths.
   static ChromePluginPlaceholder* CreateBlockedPlugin(
       content::RenderFrame* render_frame,
       blink::WebLocalFrame* frame,
@@ -26,7 +28,8 @@ class ChromePluginPlaceholder : public plugins::LoadablePluginPlaceholder,
       const base::string16& name,
       int resource_id,
       const base::string16& message,
-      const GURL& poster_url);
+      const std::string& poster_attribute,
+      const GURL& base_url);
 
   // Creates a new WebViewPlugin with a MissingPlugin as a delegate.
   static ChromePluginPlaceholder* CreateMissingPlugin(

chrome/renderer/plugins/plugin_preroller.cc

@@ -61,7 +61,7 @@ void PluginPreroller::OnThrottleStateChange() {
   ChromePluginPlaceholder* placeholder =
       ChromePluginPlaceholder::CreateBlockedPlugin(
           render_frame(), frame_, params_, info_, identifier_, name_,
-          IDR_PLUGIN_POSTER_HTML, message_, keyframe_data_url_);
+          IDR_PLUGIN_POSTER_HTML, message_, keyframe_data_url_.spec(), GURL());
   placeholder->SetPremadePlugin(throttler_);
   placeholder->set_power_saver_enabled(true);
   placeholder->set_allow_loading(true);

chrome/renderer/resources/plugin_poster.html

@@ -19,18 +19,19 @@ document.onkeydown = function(e) {
 <link rel="stylesheet" href="plugin_placeholders.css"></link>
 <style>
 #outer {
+  position: relative;
   border: none;
   cursor: pointer;
-  background-position: center;
-  background-repeat: no-repeat;
-  background-size: contain;
 }
 
 #shielding {
   background-color: rgba(0, 0, 0, 0.5);
-  height: 100%;
   position: absolute;
+  top: 0px;
+  left: 0px;
+  height: 100%;
   width: 100%;
+  z-index: 2;
 }
 
 #plugin_icon {
@@ -41,15 +42,22 @@ document.onkeydown = function(e) {
   opacity: 0.95;
 }
 
+#poster {
+  height: 100%;
+  width: 100%;
+  z-index: 1;
+}
+
 #inner {
   margin-top: -25px;
 }
 </style>
+<base i18n-values="href:baseurl">
 </head>
 
 <body onload="notifyDidFinishLoading();">
-  <div i18n-values="title:name;.style.background-image:background" id="outer"
-       onclick="plugin.load()">
+  <div i18n-values="title:name" id="outer" onclick="plugin.load()">
+    <img id="poster" i18n-values="srcset:poster">
     <div id="shielding">
       <div id="inner">
         <div><img id="plugin_icon" src="plugin_power_saver_play.png" /></div>

components/plugins/renderer/plugin_placeholder.cc

@@ -22,6 +22,8 @@ PluginPlaceholder::PluginPlaceholder(content::RenderFrame* render_frame,
                                     render_frame->GetWebkitPreferences(),
                                     html_data,
                                     placeholderDataUrl)) {
+  DCHECK(placeholderDataUrl.is_valid())
+      << "Blink requires the placeholder to have a valid URL.";
 }
 
 PluginPlaceholder::~PluginPlaceholder() {}

components/plugins/renderer/webview_plugin.cc

@@ -109,8 +109,13 @@ WebPluginContainer* WebViewPlugin::container() const { return container_; }
 
 bool WebViewPlugin::initialize(WebPluginContainer* container) {
   container_ = container;
-  if (container_)
+  if (container_) {
     old_title_ = container_->element().getAttribute("title");
+
+    // Propagate device scale to inner webview to load the correct resource
+    // when images have a "srcset" attribute.
+    web_view_->setDeviceScaleFactor(container_->deviceScaleFactor());
+  }
   return true;
 }
 
@@ -136,8 +141,14 @@ void WebViewPlugin::paint(WebCanvas* canvas, const WebRect& rect) {
 
   paint_rect.Offset(-rect_.x(), -rect_.y());
 
-  canvas->translate(SkIntToScalar(rect_.x()), SkIntToScalar(rect_.y()));
   canvas->save();
+  canvas->translate(SkIntToScalar(rect_.x()), SkIntToScalar(rect_.y()));
+
+  // Apply inverse device scale factor, as the outer webview has already
+  // applied it, and the inner webview will apply it again.
+  SkScalar inverse_scale =
+      SkFloatToScalar(1.0 / container_->deviceScaleFactor());
+  canvas->scale(inverse_scale, inverse_scale);
 
   web_view_->layout();
   web_view_->paint(canvas, paint_rect);