[Mac] Handle a child frame for TextInputClientMac

This CL fixes the problem that GetCharacterIndexAtPoint or
GetFirstRectForRange from TextInputClientMac couldn't handle a child
widget. When TextInputClientMac requests mojo calls for them, it
tries to find the focused frame but it couldn't handle a child widget
since it uses RenderViewHostImpl and RenderViewHostImpl is nullptr
when the widget's owner_delegate is empty. So, it introduces
GetFrameTree to RenderWidgetHostDelegate, gets FrameTree* through
the method, and finds the focused RenderFrameHostImpl using FrameTree.

Bug: 1094841, 1007365
Change-Id: I8da969886ef8d99347c09ae226bcbdeefc84ec0a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2245450Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Julie Kim <jkim@igalia.com>
Cr-Commit-Position: refs/heads/master@{#781099}

content/browser/renderer_host/render_widget_host_delegate.cc

@@ -162,4 +162,8 @@ bool RenderWidgetHostDelegate::IsPortal() {
   return false;
 }
 
+FrameTree* RenderWidgetHostDelegate::GetFrameTree() {
+  return nullptr;
+}
+
 }  // namespace content

content/browser/renderer_host/render_widget_host_delegate.h

@@ -42,6 +42,7 @@ class Sample;
 namespace content {
 
 class BrowserAccessibilityManager;
+class FrameTree;
 class RenderFrameHostImpl;
 class RenderWidgetHostImpl;
 class RenderWidgetHostInputEventRouter;
@@ -338,6 +339,12 @@ class CONTENT_EXPORT RenderWidgetHostDelegate {
   // Notify the delegate that the screen orientation has been changed.
   virtual void DidChangeScreenOrientation() {}
 
+  // Returns the FrameTree that this RenderWidgetHost is attached to. If the
+  // RenderWidgetHost is attached to a frame, then its RenderFrameHost will be
+  // in the tree. Otherwise, the RenderWidgetHost is for a popup which was
+  // opened by a frame in the FrameTree.
+  virtual FrameTree* GetFrameTree();
+
  protected:
   virtual ~RenderWidgetHostDelegate() {}
 };

content/browser/renderer_host/text_input_client_mac.mm

@@ -13,8 +13,6 @@
 #include "content/browser/frame_host/frame_tree.h"
 #include "content/browser/frame_host/frame_tree_node.h"
 #include "content/browser/frame_host/render_frame_host_impl.h"
-#include "content/browser/renderer_host/render_view_host_delegate.h"
-#include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/renderer_host/render_widget_host_delegate.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/common/text_input_client_messages.h"
@@ -52,15 +50,14 @@ bool IsFullScreenRenderWidget(RenderWidgetHost* widget) {
 }
 
 RenderFrameHostImpl* GetFocusedRenderFrameHostImpl(RenderWidgetHost* widget) {
-  RenderViewHostImpl* rvhi = RenderViewHostImpl::From(widget);
-  if (!rvhi || !rvhi->GetDelegate()->GetFrameTree())
-    return nullptr;
-  FrameTreeNode* frame_tree_node =
-      rvhi->GetDelegate()->GetFrameTree()->GetFocusedFrame();
-  return frame_tree_node ? frame_tree_node->current_frame_host() : nullptr;
-}
+  RenderWidgetHostImpl* rwhi = RenderWidgetHostImpl::From(widget);
+  FrameTree* tree = rwhi->delegate()->GetFrameTree();
+  FrameTreeNode* focused_node = tree->GetFocusedFrame();
+  return focused_node ? focused_node->current_frame_host() : nullptr;
 }
 
+}  // namespace
+
 // The amount of time in milliseconds that the browser process will wait for a
 // response from the renderer.
 // TODO(rsesek): Using the histogram data, find the best upper-bound for this

content/browser/web_contents/web_contents_impl.h

@@ -924,6 +924,9 @@ class CONTENT_EXPORT WebContentsImpl : public WebContents,
   bool AddDomainInfoToRapporSample(rappor::Sample* sample) override;
   bool IsShowingContextMenuOnPage() const override;
   void DidChangeScreenOrientation() override;
+  // The following function is already listed under RenderViewHostDelegate
+  // overrides:
+  // FrameTree* GetFrameTree() override;
 
   // RenderFrameHostManager::Delegate ------------------------------------------