Fixes crash if instant is enabled and you block JS.

chrome/renderer/searchbox_extension.cc

 // Copyright (c) 2010 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 "chrome/renderer/searchbox_extension.h"
 
 #include <string>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 336 matching lines @@
   return v8::Undefined();
 }
 
 // static
 bool Dispatch(WebFrame* frame, const std::string& event_name) {
   DCHECK(frame) << "Dispatch requires frame";
   if (!frame) return false;
 
   v8::HandleScope handle_scope;
   v8::Local<v8::Context> context = frame->mainWorldScriptContext();
+  if (context.IsEmpty())
+    return false;
   v8::Context::Scope context_scope(context);
 
   v8::Local<v8::Value> value =
       context->Global()->Get(v8::String::New("window"));
   std::vector<std::string> components;
   base::SplitStringDontTrim(event_name, '.', &components);
   for (size_t i = 0; i < components.size(); ++i) {
     if (!value.IsEmpty() && value->IsObject())
       value = value->ToObject()->Get(v8::String::New(components[i].c_str()));
   }
@@ skipping 34 matching lines @@
   if (Dispatch(frame, kResizeEventName))
     return;
   frame->executeScript(WebScriptSource(kSetOmniboxBoundsScript));
 }
 
 // static
 bool SearchBoxExtension::PageSupportsInstant(WebFrame* frame) {
   DCHECK(frame) << "PageSupportsInstant requires frame";
   if (!frame) return false;
 
-  bool supports_deprecated_api = frame->executeScriptAndReturnValue(
-      WebScriptSource(kSupportsInstantScript))->BooleanValue();
+  v8::Handle<v8::Value> v = frame->executeScriptAndReturnValue(
+      WebScriptSource(kSupportsInstantScript));
+  bool supports_deprecated_api = !v.IsEmpty() && v->BooleanValue();
   // TODO(tonyg): Add way of detecting instant support to SearchBox API.
   bool supports_searchbox_api = supports_deprecated_api;
 
   // The deprecated API needs to notify the page of events it may have missed.
   // This isn't necessary in the SearchBox API, since the page can query the
   // API at any time.
   static std::string init_script(
       StringPrintf(kInitScript, kSetOmniboxBoundsScript, kUserInputScript));
   if (supports_deprecated_api) {
     frame->executeScript(WebScriptSource(WebString::fromUTF8(init_script)));
   }
 
   return supports_searchbox_api || supports_deprecated_api;
 }
 
 // static
 v8::Extension* SearchBoxExtension::Get() {
   return new SearchBoxExtensionWrapper();
 }
 
 }  // namespace extensions_v8