Use V8 Maybe APIs in extensions/renderer

extensions/renderer/file_system_natives.cc

Index: extensions/renderer/file_system_natives.cc
diff --git a/extensions/renderer/file_system_natives.cc b/extensions/renderer/file_system_natives.cc
index a06eec8cdd35de2a7cc30b80f18a75e2c3f93b3a..adb5165dfa1f88fa8dfa1867da44456bfa57b3a9 100644
--- a/extensions/renderer/file_system_natives.cc
+++ b/extensions/renderer/file_system_natives.cc
@@ -8,6 +8,7 @@
 
 #include "extensions/common/constants.h"
 #include "extensions/renderer/script_context.h"
+#include "extensions/renderer/v8_maybe_helpers.h"
 #include "storage/common/fileapi/file_system_types.h"
 #include "storage/common/fileapi/file_system_util.h"
 #include "third_party/WebKit/public/platform/WebString.h"
@@ -91,8 +92,9 @@ void FileSystemNatives::GetFileEntry(
 
   DCHECK(args[4]->IsBoolean());
   blink::WebDOMFileSystem::EntryType entry_type =
-      args[4]->BooleanValue() ? blink::WebDOMFileSystem::EntryTypeDirectory
-                              : blink::WebDOMFileSystem::EntryTypeFile;
+      args[4].As<v8::Boolean>()->Value()
+          ? blink::WebDOMFileSystem::EntryTypeDirectory
+          : blink::WebDOMFileSystem::EntryTypeFile;
 
   blink::WebLocalFrame* webframe =
       blink::WebLocalFrame::frameForContext(context()->v8_context());
@@ -117,11 +119,11 @@ void FileSystemNatives::CrackIsolatedFileSystemName(
   std::string filesystem_id;
   if (!storage::CrackIsolatedFileSystemName(filesystem_name, &filesystem_id))
     return;
+  if (filesystem_id.size() >= v8::String::kMaxLength)
+    return;
 
-  args.GetReturnValue().Set(v8::String::NewFromUtf8(args.GetIsolate(),
-                                                    filesystem_id.c_str(),
-                                                    v8::String::kNormalString,
-                                                    filesystem_id.size()));
+  args.GetReturnValue().Set(
+      ToV8String(args.GetIsolate(), filesystem_id.c_str()));
 }
 
 void FileSystemNatives::GetDOMError(