[cleanup] fix ChromeOs uses of ToBoolean/ToObject

Remove uses of deprecated functions in
file_browser_handler_custom_bindings.cc, replacing ToObject() on a
known Object with .As<v8::Object>() and use the Context form of
ToBoolean along with FromMaybe(false)

Bug: v8:7786
Change-Id: Ib4726f5ae77797c736e35d36ae0ca25f50808a0a
Reviewed-on: https://chromium-review.googlesource.com/1172436Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582864}

chrome/renderer/extensions/file_browser_handler_custom_bindings.cc

@@ -35,7 +35,7 @@ void FileBrowserHandlerCustomBindings::GetExternalFileEntry(
 #if defined(OS_CHROMEOS)
     CHECK(args.Length() == 1);
     CHECK(args[0]->IsObject());
-    v8::Local<v8::Object> file_def = args[0]->ToObject();
+    v8::Local<v8::Object> file_def = args[0].As<v8::Object>();
     v8::Isolate* isolate = args.GetIsolate();
     std::string file_system_name(*v8::String::Utf8Value(
         isolate,
@@ -48,8 +48,8 @@ void FileBrowserHandlerCustomBindings::GetExternalFileEntry(
         file_def->Get(v8::String::NewFromUtf8(isolate, "fileFullPath"))));
     bool is_directory =
         file_def->Get(v8::String::NewFromUtf8(isolate, "fileIsDirectory"))
-            ->ToBoolean()
-            ->Value();
+            ->BooleanValue(context->v8_context())
+            .FromMaybe(false);
     blink::WebDOMFileSystem::EntryType entry_type =
         is_directory ? blink::WebDOMFileSystem::kEntryTypeDirectory
                      : blink::WebDOMFileSystem::kEntryTypeFile;