Enable -Wimplicit-fallthrough on Android.

Fixes a bug where vr_shell counted VRMode::VR_BROWSER also as
VRMode::WEBVR and VRMode::VR_FULLSCREEN, and VRMode::WEBVR also
as VRMode::VR_FULLSCREEN in rappor.

Bug: 177475
Change-Id: I23a0c2b5fb94d34d407070ef0a9378d02fe4ba54
Reviewed-on: https://chromium-review.googlesource.com/899722Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534124}

build/config/compiler/BUILD.gn

@@ -1429,7 +1429,8 @@ config("chromium_code") {
   # Warn on missing break statements at the end of switch cases.
   # For intentional fallthrough, use FALLTHROUGH; from base/compiler_specific.h
   # TODO(thakis): Enable for all platforms, https://crbug.com/177475
-  if (is_clang && (is_fuchsia || (is_linux && !is_chromecast && !use_ozone))) {
+  if (is_clang &&
+      (is_android || is_fuchsia || (is_linux && !is_chromecast && !use_ozone))) {
     cflags += [ "-Wimplicit-fallthrough" ]
   }
 

chrome/browser/android/browsing_data/browsing_data_bridge.cc

@@ -112,6 +112,7 @@ static void JNI_BrowsingDataBridge_ClearBrowsingData(
       case browsing_data::BrowsingDataType::HOSTED_APPS_DATA:
         // Only implemented on Desktop.
         NOTREACHED();
+        FALLTHROUGH;
       case browsing_data::BrowsingDataType::NUM_TYPES:
         NOTREACHED();
     }

chrome/browser/android/vr_shell/vr_metrics_util.cc

@@ -38,7 +38,8 @@ void VrMetricsUtil::LogGvrVersionForVrViewerType(
         encoded_version = kGvrTooOld;
         break;
       }
-    // Fall through since a version can be logged in this case.
+      // Fall through since a version can be logged in this case.
+      FALLTHROUGH;
     case VrCoreCompatibility::VR_CORE_COMPATIBILITY_VR_READY:
       encoded_version =
           std::min(vr_core_info.gvr_sdk_version.major, 999) * 1000 * 1000 +

chrome/browser/android/vr_shell/vr_usage_monitor.cc

@@ -107,6 +107,7 @@ void SendRapporEnteredMode(const GURL& origin, vr::Mode mode) {
     case vr::Mode::kVrBrowsingFullscreen:
       rappor::SampleDomainAndRegistryFromGURL(rappor::GetDefaultService(),
                                               "VR.FullScreenMode", origin);
+      break;
     default:
       break;
   }
@@ -117,12 +118,15 @@ void SendRapporEnteredVideoMode(const GURL& origin, vr::Mode mode) {
     case vr::Mode::kVrBrowsingRegular:
       rappor::SampleDomainAndRegistryFromGURL(rappor::GetDefaultService(),
                                               "VR.Video.Browser", origin);
+      break;
     case vr::Mode::kWebVr:
       rappor::SampleDomainAndRegistryFromGURL(rappor::GetDefaultService(),
                                               "VR.Video.WebVR", origin);
+      break;
     case vr::Mode::kVrBrowsingFullscreen:
       rappor::SampleDomainAndRegistryFromGURL(
           rappor::GetDefaultService(), "VR.Video.FullScreenMode", origin);
+      break;
     default:
       break;
   }

chrome/browser/download/chrome_download_manager_delegate.cc

@@ -806,7 +806,7 @@ void ChromeDownloadManagerDelegate::RequestConfirmation(
             download, suggested_path, callback);
         return;
       }
-    // Fallthrough
+      FALLTHROUGH;
 
     // If we cannot reserve the path and the WebContent is already gone, there
     // is no way to prompt user for an infobar. This could happen after chrome

chrome/browser/geolocation/geolocation_permission_context_android.cc

@@ -310,7 +310,7 @@ void GeolocationPermissionContextAndroid::UpdateLocationSettingsBackOff(
       break;
     case LocationSettingsDialogBackOff::kOneMonth:
       backoff_level = LocationSettingsDialogBackOff::kThreeMonths;
-    // fall through
+      FALLTHROUGH;
     case LocationSettingsDialogBackOff::kThreeMonths:
       next_show += base::TimeDelta::FromDays(90);
       break;

chrome/browser/ui/page_info/page_info_ui.cc

@@ -208,11 +208,12 @@ PageInfoUI::IdentityInfo::GetSecurityDescription() const {
       return CreateSecurityDescription(SecuritySummaryColor::GREEN,
                                        IDS_PAGE_INFO_INTERNAL_PAGE,
                                        IDS_PAGE_INFO_INTERNAL_PAGE);
-#endif
+#else
       // Internal pages on desktop have their own UI implementations which
       // should never call this function.
       NOTREACHED();
       FALLTHROUGH;
+#endif
     case PageInfo::SITE_IDENTITY_STATUS_CERT:
     case PageInfo::SITE_IDENTITY_STATUS_EV_CERT:
     case PageInfo::SITE_IDENTITY_STATUS_CERT_REVOCATION_UNKNOWN:

content/browser/renderer_host/render_widget_host_view_android.cc

@@ -2397,6 +2397,7 @@ void RenderWidgetHostViewAndroid::ComputeEventLatencyOSTouchHistograms(
     case ui::MotionEvent::ACTION_POINTER_UP:
       UMA_HISTOGRAM_CUSTOM_COUNTS("Event.Latency.OS.TOUCH_RELEASED",
                                   delta.InMicroseconds(), 1, 1000000, 50);
+      return;
     default:
       return;
   }