Make WebDocument's use of Document::GetExecutionContext() safe

There are 4 places Document::GetExecutionContext() is currently
invoked in WebDocument:
* GetSecurityOrigin() is the only one of the 4 that null-checks it.
* OutgoingReferrer() is unused and can be removed.
* GetReferrerPolicy() has a single use that can easily be adjusted so
  that it can be removed.
* IsSecureContext() needs a null-check.

Bug: 1121726
Change-Id: I0f65a56909e4bc1a5ee6aee30e0e59c8c698b434
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2375704
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Auto-Submit: Nate Chapin <japhet@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801618}

third_party/blink/public/web/web_document.h

@@ -104,8 +104,6 @@ class WebDocument : public WebNode {
   BLINK_EXPORT WebURL CompleteURL(const WebString&) const;
   BLINK_EXPORT WebElement GetElementById(const WebString&) const;
   BLINK_EXPORT WebElement FocusedElement() const;
-  BLINK_EXPORT network::mojom::ReferrerPolicy GetReferrerPolicy() const;
-  BLINK_EXPORT WebString OutgoingReferrer();
 
   // Inserts the given CSS source code as a style sheet in the document.
   BLINK_EXPORT WebStyleSheetKey InsertStyleSheet(

third_party/blink/renderer/core/exported/web_document.cc

@@ -93,7 +93,9 @@ WebSecurityOrigin WebDocument::GetSecurityOrigin() const {
 
 bool WebDocument::IsSecureContext() const {
   const Document* document = ConstUnwrap<Document>();
-  return document && document->GetExecutionContext()->IsSecureContext();
+  ExecutionContext* context =
+      document ? document->GetExecutionContext() : nullptr;
+  return context && context->IsSecureContext();
 }
 
 WebString WebDocument::Encoding() const {
@@ -235,15 +237,6 @@ void WebDocument::WatchCSSSelectors(const WebVector<WebString>& web_selectors) {
   CSSSelectorWatch::From(*document).WatchCSSSelectors(selectors);
 }
 
-network::mojom::ReferrerPolicy WebDocument::GetReferrerPolicy() const {
-  return ConstUnwrap<Document>()->GetExecutionContext()->GetReferrerPolicy();
-}
-
-WebString WebDocument::OutgoingReferrer() {
-  return WebString(
-      Unwrap<Document>()->GetExecutionContext()->OutgoingReferrer());
-}
-
 WebVector<WebDraggableRegion> WebDocument::DraggableRegions() const {
   WebVector<WebDraggableRegion> draggable_regions;
   const Document* document = ConstUnwrap<Document>();

third_party/blink/renderer/core/page/chrome_client_impl.cc

@@ -238,9 +238,7 @@ void ChromeClientImpl::StartDragging(LocalFrame* frame,
                                      const SkBitmap& drag_image,
                                      const gfx::Point& drag_image_offset) {
   WebLocalFrameImpl* web_frame = WebLocalFrameImpl::FromFrame(frame);
-  WebDragData drag = drag_data;
-  drag.SetReferrerPolicy(web_frame->GetDocument().GetReferrerPolicy());
-  web_frame->LocalRootFrameWidget()->StartDragging(drag, mask, drag_image,
+  web_frame->LocalRootFrameWidget()->StartDragging(drag_data, mask, drag_image,
                                                    drag_image_offset);
 }
 

third_party/blink/renderer/core/page/drag_controller.cc

@@ -1334,6 +1334,7 @@ void DragController::DoSystemDrag(DragImage* image,
   IntSize offset_size(adjusted_event_pos - adjusted_drag_location);
   gfx::Point offset_point(offset_size.Width(), offset_size.Height());
   WebDragData drag_data = data_transfer->GetDataObject()->ToWebDragData();
+  drag_data.SetReferrerPolicy(drag_initiator_->GetReferrerPolicy());
   WebDragOperationsMask drag_operation_mask =
       static_cast<WebDragOperationsMask>(data_transfer->SourceOperation());
   SkBitmap drag_image;