Reland "Correctly set ScriptState in the image loader microtask"

Source/core/dom/Microtask.h

Index: Source/core/dom/Microtask.h
diff --git a/Source/core/dom/Microtask.h b/Source/core/dom/Microtask.h
index e2c86bbc226392a47d1d6caa2d793c23756a27b9..e111c03da1dac1d1b06913a2c62c37b97c434e99 100644
--- a/Source/core/dom/Microtask.h
+++ b/Source/core/dom/Microtask.h
@@ -44,6 +44,10 @@ class CORE_EXPORT Microtask {
 public:
     static void performCheckpoint(v8::Isolate*);
     static bool performingCheckpoint(v8::Isolate*);
+
+    // TODO(jochen): Make all microtasks pass in the ScriptState they want to be
+    // executed in. Until then, all microtasks have to keep track of their
+    // ScriptState themselves.
     static void enqueueMicrotask(PassOwnPtr<WebThread::Task>);
     static void enqueueMicrotask(PassOwnPtr<Closure>);