Add some CHECKs to PepperPDFHost to figure out a crash.

components/pdf/renderer/pepper_pdf_host.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 "components/pdf/renderer/pepper_pdf_host.h"
 
 #include "components/pdf/common/pdf_messages.h"
 #include "components/pdf/renderer/pdf_accessibility_tree.h"
 #include "content/public/common/referrer.h"
 #include "content/public/renderer/pepper_plugin_instance.h"
@@ skipping 124 matching lines @@
   return PP_OK;
 }
 
 int32_t PepperPDFHost::OnHostMsgHasUnsupportedFeature(
     ppapi::host::HostMessageContext* context) {
   content::PepperPluginInstance* instance =
       host_->GetPluginInstance(pp_instance());
   if (!instance)
     return PP_ERROR_FAILED;
 
+  // TODO(thestig): Turn CHECKs into the proper if statement after figuring out
+  // what's wrong for https://crbug.com/627814
+  CHECK(instance->GetContainer());
+  CHECK(instance->GetContainer()->document().frame());
+  CHECK(instance->GetContainer()->document().frame()->view());
   blink::WebView* view =
       instance->GetContainer()->document().frame()->view();
   content::RenderView* render_view = content::RenderView::FromWebView(view);
   render_view->Send(
       new PDFHostMsg_PDFHasUnsupportedFeature(render_view->GetRoutingID()));
   return PP_OK;
 }
 
 int32_t PepperPDFHost::OnHostMsgPrint(
     ppapi::host::HostMessageContext* context) {
@@ skipping 80 matching lines @@
 
 void PepperPDFHost::CreatePdfAccessibilityTreeIfNeeded(
     content::PepperPluginInstance* instance) {
   if (!pdf_accessibility_tree_) {
     pdf_accessibility_tree_.reset(
         new PdfAccessibilityTree(instance->GetRenderView()));
   }
 }
 
 }  // namespace pdf