Code: void AwContents::DidOverscroll(gfx::Vector2d overscroll_delta,
                               gfx::Vector2dF overscroll_velocity) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   JNIEnv* env = AttachCurrentThread();
   ScopedJavaLocalRef<jobject> obj = java_ref_.get(env);
  if (obj.is_null())
    return;
  Java_AwContents_didOverscroll(env, obj.obj(), overscroll_delta.x(),
                                overscroll_delta.y(), overscroll_velocity.x(),
                                overscroll_velocity.y());
}

Vulnerability Type: DoS 
CWE ID: CWE-399
Summary: Use-after-free vulnerability in the StyleElement::removedFromDocument function in core/dom/StyleElement.cpp in Blink, as used in Google Chrome before 35.0.1916.114, allows remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact via crafted JavaScript code that triggers tree mutation.
Commit Message: sync compositor: pass simple gfx types by const ref

See bug for reasoning

BUG=159273

Review URL: https://codereview.chromium.org/1417893006

Cr-Commit-Position: refs/heads/master@{#356653}