TextInputManager::GetTextSelection() should be called on focused widget.

content/browser/frame_host/render_widget_host_view_child_frame.cc

 // Copyright 2014 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/frame_host/render_widget_host_view_child_frame.h"
 
 #include <algorithm>
 #include <utility>
 #include <vector>
 
@@ skipping 38 matching lines @@
       frame_connector_(nullptr),
       begin_frame_source_(nullptr),
       observing_begin_frame_source_(false),
       parent_surface_client_id_(0),
       weak_factory_(this) {
   id_allocator_.reset(new cc::SurfaceIdAllocator(AllocateSurfaceClientId()));
   GetSurfaceManager()->RegisterSurfaceClientId(id_allocator_->client_id());
   RegisterSurfaceNamespaceId();
 
   host_->SetView(this);
+  GetTextInputManager();

[EhsanK, 2016/08/20 02:41:30]

This initialization is necessary because InputMethodChromeOS calls
GetTextSelection() on the focused view which has not yet initialized its
|text_input_manager_|. This was firing the DCHECK in
TextInputManager::GetTextSelection.

 }
 
 RenderWidgetHostViewChildFrame::~RenderWidgetHostViewChildFrame() {
   if (!surface_id_.is_null())
     surface_factory_->Destroy(surface_id_);
 
   if (GetSurfaceManager())
     GetSurfaceManager()->InvalidateSurfaceClientId(id_allocator_->client_id());
 }
 
@@ skipping 652 matching lines @@
 
 bool RenderWidgetHostViewChildFrame::IsChildFrameForTesting() const {
   return true;
 }
 
 cc::SurfaceId RenderWidgetHostViewChildFrame::SurfaceIdForTesting() const {
   return surface_id_;
 };
 
 }  // namespace content