Remove usages of WebContents::GetRenderViewHost().

This CL was uploaded by git cl split.

R=wjmaclean@chromium.org

Bug: 1142671
Change-Id: If0a13494ab772d5f980c13fe37cfab186f99e26c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2501122
Auto-Submit: Lucas Gadani <lfg@chromium.org>
Reviewed-by: James MacLean <wjmaclean@chromium.org>
Commit-Queue: James MacLean <wjmaclean@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821232}

chrome/browser/ui/zoom/zoom_controller_browsertest.cc

@@ -87,7 +87,8 @@ IN_PROC_BROWSER_TEST_F(ZoomControllerBrowserTest,
     host->Shutdown(0);
     crash_observer.Wait();
   }
-  EXPECT_FALSE(web_contents->GetRenderViewHost()->IsRenderViewLive());
+  EXPECT_FALSE(
+      web_contents->GetMainFrame()->GetRenderViewHost()->IsRenderViewLive());
 
   // The following attempt to change the zoom level for a crashed tab should
   // fail.