Add missing null checks in permissions code

This CL adds a couple of missing null checks in permissions code to
handle the case where a RenderFrameHost has already been destroyed.

Bug: 754585
Change-Id: I1d009b8ec5776421462cba05ecfb499a51034b10
Reviewed-on: https://chromium-review.googlesource.com/1077878Reviewed-by: Raymes Khoury <raymes@chromium.org>
Commit-Queue: Timothy Loh <timloh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563137}

chrome/browser/geolocation/geolocation_permission_context_android.cc

@@ -188,6 +188,8 @@ void GeolocationPermissionContextAndroid::NotifyPermissionSet(
         content::WebContents::FromRenderFrameHost(
             content::RenderFrameHost::FromID(id.render_process_id(),
                                              id.render_frame_id()));
+    if (!web_contents)
+      return;
 
     // Only show the location settings dialog if the tab for |web_contents| is
     // user-interactable (i.e. is the current tab, and Chrome is active and not

chrome/browser/plugins/flash_permission_context.cc

@@ -64,6 +64,8 @@ void FlashPermissionContext::UpdateTabContext(const PermissionRequestID& id,
       content::WebContents::FromRenderFrameHost(
           content::RenderFrameHost::FromID(id.render_process_id(),
                                            id.render_frame_id()));
+  if (!web_contents)
+    return;
 
   if (PluginsEnterpriseSettingEnabled(
           HostContentSettingsMapFactory::GetForProfile(profile()))) {