[WebView] Remove dependencies on DebugFlags. BUG:18152150 Change-Id: Ifafa06a01db4a679b9777798f3bdeda0abc3021e (cherry picked from commit 4eb3b4bdb57147426190c8fb42a7b5c33a0a2857) (cherry picked from commit 53cb980b31715024c38abc06a5147918ca937e39)