Add temporary check to debug issue 731239.

This check asserts that the main frame's SecurityOrigin hasn't changed
between updating the plugin list and accessing the DOMPluginArray.

Bug: 731239
Change-Id: Ifa247045f1415d6b593fd18f626b1ddc37222aec
Reviewed-on: https://chromium-review.googlesource.com/531994Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Lucas Furukawa Gadani <lfg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#478830}

third_party/WebKit/Source/modules/plugins/DOMPluginArray.cpp

@@ -47,6 +47,9 @@ unsigned DOMPluginArray::length() const {
 }
 
 DOMPlugin* DOMPluginArray::item(unsigned index) {
+  // TODO(lfg): Temporary to track down https://crbug.com/731239.
+  CHECK(main_frame_origin_->IsSameSchemeHostPort(GetPluginData()->Origin()));
+
   if (index >= dom_plugins_.size())
     return nullptr;
   if (!dom_plugins_[index]) {
@@ -107,6 +110,8 @@ void DOMPluginArray::UpdatePluginData() {
     return;
   }
 
+  main_frame_origin_ = data->Origin();
+
   HeapVector<Member<DOMPlugin>> old_dom_plugins(std::move(dom_plugins_));
   dom_plugins_.clear();
   dom_plugins_.resize(data->Plugins().size());

third_party/WebKit/Source/modules/plugins/DOMPluginArray.h

@@ -25,6 +25,7 @@
 #include "modules/plugins/DOMPlugin.h"
 #include "platform/bindings/ScriptWrappable.h"
 #include "platform/heap/Handle.h"
+#include "platform/weborigin/SecurityOrigin.h"
 #include "platform/wtf/Forward.h"
 
 namespace blink {
@@ -32,7 +33,7 @@ namespace blink {
 class LocalFrame;
 class PluginData;
 
-class DOMPluginArray final : public GarbageCollected<DOMPluginArray>,
+class DOMPluginArray final : public GarbageCollectedFinalized<DOMPluginArray>,
                              public ScriptWrappable,
                              public ContextClient {
   DEFINE_WRAPPERTYPEINFO();
@@ -57,6 +58,9 @@ class DOMPluginArray final : public GarbageCollected<DOMPluginArray>,
   PluginData* GetPluginData() const;
 
   HeapVector<Member<DOMPlugin>> dom_plugins_;
+
+  // TODO(lfg): Temporary to track down https://crbug.com/731239.
+  RefPtr<const SecurityOrigin> main_frame_origin_;
 };
 
 }  // namespace blink