[unseasoned-pdf] Add PdfViewWebPlugin::GetValidContainerFrame().

Getting the access to the document's WebLocalFrame is often needed in
PdfViewWebPlugin, therefore add a helper function
GetValidContainerFrame() which checks for a valid WebLocalFrame and
returns it.

Change-Id: Ib026b69377ecc0378013677cae44192cec1f7ab4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2870487
Commit-Queue: Hui Yingst <nigi@chromium.org>
Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#878750}

pdf/pdf_view_web_plugin.cc

@@ -394,17 +394,13 @@ net::SiteForCookies PdfViewWebPlugin::SiteForCookies() const {
 void PdfViewWebPlugin::SetReferrerForRequest(
     blink::WebURLRequest& request,
     const blink::WebURL& referrer_url) {
-  DCHECK(IsValid());
-  Container()->GetDocument().GetFrame()->SetReferrerForRequest(request,
-                                                               referrer_url);
+  GetValidContainerFrame()->SetReferrerForRequest(request, referrer_url);
 }
 
 std::unique_ptr<blink::WebAssociatedURLLoader>
 PdfViewWebPlugin::CreateAssociatedURLLoader(
     const blink::WebAssociatedURLLoaderOptions& options) {
-  DCHECK(IsValid());
-  return Container()->GetDocument().GetFrame()->CreateAssociatedURLLoader(
-      options);
+  return GetValidContainerFrame()->CreateAssociatedURLLoader(options);
 }
 
 void PdfViewWebPlugin::OnMessage(const base::Value& message) {
@@ -503,6 +499,11 @@ void PdfViewWebPlugin::UserMetricsRecordAction(const std::string& action) {
   base::RecordAction(base::UserMetricsAction(action.c_str()));
 }
 
+blink::WebLocalFrame* PdfViewWebPlugin::GetValidContainerFrame() const {
+  DCHECK(IsValid());
+  return Container()->GetDocument().GetFrame();
+}
+
 void PdfViewWebPlugin::OnViewportChanged(const gfx::Rect& view_rect,
                                          float new_device_scale) {
   UpdateGeometryOnViewChanged(view_rect, new_device_scale);

pdf/pdf_view_web_plugin.h

@@ -19,6 +19,7 @@
 #include "v8/include/v8.h"
 
 namespace blink {
+class WebLocalFrame;
 class WebPluginContainer;
 }  // namespace blink
 
@@ -153,6 +154,10 @@ class PdfViewWebPlugin final : public PdfViewPluginBase,
 
   bool InitializeCommon(std::unique_ptr<ContainerWrapper> container_wrapper);
 
+  // Returns the local frame to which the web plugin container belongs to. May
+  // only be called when the plugin has the container inside a valid frame.
+  blink::WebLocalFrame* GetValidContainerFrame() const;
+
   void OnViewportChanged(const gfx::Rect& view_rect, float new_device_scale);
 
   // Invalidates the entire web plugin container and schedules a paint of the