Make GreasemonkeyApiJsString truly singleton.

extensions/renderer/user_script_injector.cc

Index: extensions/renderer/user_script_injector.cc
diff --git a/extensions/renderer/user_script_injector.cc b/extensions/renderer/user_script_injector.cc
index 0b2184a18b58ec7ccf556edf24f11ec7f56a32b9..d036f6c633f029d632f049d73f5542c6d024ca23 100644
--- a/extensions/renderer/user_script_injector.cc
+++ b/extensions/renderer/user_script_injector.cc
@@ -65,19 +65,22 @@ struct GreasemonkeyApiJsString {
   blink::WebScriptSource GetSource() const;
 
  private:
-  std::string source_;
+  // Data is owned by ResourceBundle.

[Devlin, 2016/08/20 01:58:36]

Not quite true, right? fromUTF8() still performs a copy of the data and makes a
refcounted storage (so this initial copy is the only one), but the data will be
owned by WebString storage.

So I would just omit this comment entirely.

[lazyboy, 2016/08/22 17:09:50]

That's right. Removed the comment.
 fromUTF8() still performs a copy of the data and makes a

+  blink::WebString source_;
 };
 
 // The below constructor, monstrous as it is, just makes a WebScriptSource from
 // the GreasemonkeyApiJs resource.
-GreasemonkeyApiJsString::GreasemonkeyApiJsString()
-    : source_(ResourceBundle::GetSharedInstance()
-                  .GetRawDataResource(IDR_GREASEMONKEY_API_JS)
-                  .as_string()) {
+GreasemonkeyApiJsString::GreasemonkeyApiJsString() {
+  base::StringPiece source_piece =
+      ResourceBundle::GetSharedInstance().GetRawDataResource(
+          IDR_GREASEMONKEY_API_JS);
+  source_ =
+      blink::WebString::fromUTF8(source_piece.data(), source_piece.length());
 }
 
 blink::WebScriptSource GreasemonkeyApiJsString::GetSource() const {
-  return blink::WebScriptSource(blink::WebString::fromUTF8(source_));
+  return blink::WebScriptSource(source_);
 }
 
 base::LazyInstance<GreasemonkeyApiJsString> g_greasemonkey_api =