Click to Open PDF: Create PDF placeholder on mobile.

Create PDF placeholder in ChromeContentRendererClient when the
enable_plugins build flag is off. Tested manually on mobile.

Bug: 737787
Change-Id: Iddb276b8ce71c92ee7fb626115269f2730b8b943
Reviewed-on: https://chromium-review.googlesource.com/575190
Commit-Queue: Amber Won <amberwon@google.com>
Reviewed-by: Tommy Li <tommycli@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487561}

chrome/renderer/BUILD.gn

@@ -74,6 +74,8 @@ static_library("renderer") {
     "page_load_metrics/renderer_page_track_decider.h",
     "plugins/non_loadable_plugin_placeholder.cc",
     "plugins/non_loadable_plugin_placeholder.h",
+    "plugins/pdf_plugin_placeholder.cc",
+    "plugins/pdf_plugin_placeholder.h",
     "plugins/plugin_uma.cc",
     "plugins/plugin_uma.h",
     "prerender/prerender_dispatcher.cc",
@@ -194,8 +196,6 @@ static_library("renderer") {
       "pepper/pepper_uma_host.h",
       "plugins/chrome_plugin_placeholder.cc",
       "plugins/chrome_plugin_placeholder.h",
-      "plugins/pdf_plugin_placeholder.cc",
-      "plugins/pdf_plugin_placeholder.h",
       "plugins/plugin_preroller.cc",
       "plugins/plugin_preroller.h",
       "plugins/power_saver_info.cc",

chrome/renderer/chrome_content_renderer_client.cc

@@ -655,6 +655,12 @@ bool ChromeContentRendererClient::OverrideCreatePlugin(
   if (orig_mime_type == kPDFMimeType) {
     ReportPDFLoadStatus(
         PDFLoadStatus::kShowedDisabledPluginPlaceholderForEmbeddedPdf);
+    if (base::FeatureList::IsEnabled(features::kClickToOpenPDFPlaceholder)) {
+      PDFPluginPlaceholder* placeholder =
+          PDFPluginPlaceholder::CreatePDFPlaceholder(render_frame, params);
+      *plugin = placeholder->plugin();
+      return true;
+    }
   }
   auto* placeholder = NonLoadablePluginPlaceholder::CreateNotSupportedPlugin(
       render_frame, params);