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}
void AwContents::FindNext(JNIEnv* env, jobject obj, jboolean forward) {
  DCHECK_CURRENTLY_ON(BrowserThread::UI);
  GetFindHelper()->FindNext(forward);
}

void AwContents::FindNext(JNIEnv* env, jobject obj, jboolean forward) {
  DCHECK_CURRENTLY_ON(BrowserThread::UI);
  GetFindHelper()->FindNext(forward);
}
