Request composition info from the focused RenderWidget

content/browser/renderer_host/render_widget_host_view_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_view_mac.h"
 
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
 #include <stdint.h>
@@ skipping 861 matching lines @@
   // like Chrome does on Windows, call |UpdateCursor()| here.
 }
 
 void RenderWidgetHostViewMac::OnUpdateTextInputStateCalled(
     TextInputManager* text_input_manager,
     RenderWidgetHostViewBase* updated_view,
     bool did_update_state) {
   if (!did_update_state)
     return;
 
+  // |updated_view| is the last view to change its TextInputState which can be
+  // used to start/stop monitoring composition info when it has a focused
+  // editable text input field.
+  RenderWidgetHost* widgetHost = updated_view->GetRenderWidgetHost();
+
+  // We might end up here when |updated_view| has had active TextInputState and
+  // then got destroyed. In that case, |updated_view->GetRenderWidgetHost()|
+  // returns nullptr.
+  if (!widgetHost)
+    return;
+
   // Set the monitor state based on the text input focus state.
   const bool has_focus = HasFocus();
   const TextInputState* state = text_input_manager->GetTextInputState();
   bool need_monitor_composition =
       has_focus && state && state->type != ui::TEXT_INPUT_TYPE_NONE;
-  Send(new InputMsg_RequestCompositionUpdate(
-      render_widget_host_->GetRoutingID(), false /* immediate request */,
+
+  widgetHost->Send(new InputMsg_RequestCompositionUpdate(
+      widgetHost->GetRoutingID(), false /* immediate request */,
       need_monitor_composition));
 
   if (has_focus) {
     SetTextInputActive(true);
 
     // Let AppKit cache the new input context to make IMEs happy.
     // See http://crbug.com/73039.
     [NSApp updateWindows];
 
 #ifndef __LP64__
@@ skipping 2464 matching lines @@
 
 // "-webkit-app-region: drag | no-drag" is implemented on Mac by excluding
 // regions that are not draggable. (See ControlRegionView in
 // native_app_window_cocoa.mm). This requires the render host view to be
 // draggable by default.
 - (BOOL)mouseDownCanMoveWindow {
   return YES;
 }
 
 @end