[WebLayer][AW] Add SafeBrowsing.BlockingPage.ResourceType UMA

Add UMA for logging the resource type that triggers the
Safe Browsing blocking page for WebLayer and Android WebView.

Currently this histogram is logged in chrome. It is useful
in order to be able to compare usage numbers across platforms
and to obtain overall Safe Browsing usage stats.

BUG=1136072

Change-Id: I3b09f631b51d242e0fe6ab9b2421b377e25806df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2456348
Commit-Queue: Tim Volodine <timvolodine@chromium.org>
Reviewed-by: Xinghui Lu <xinghuilu@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814819}

android_webview/browser/safe_browsing/aw_safe_browsing_blocking_page.cc

@@ -93,6 +93,9 @@ AwSafeBrowsingBlockingPage* AwSafeBrowsingBlockingPage::CreateBlockingPage(
     const GURL& main_frame_url,
     const UnsafeResource& unsafe_resource,
     std::unique_ptr<AwWebResourceRequest> resource_request) {
+  // Log the resource type that triggers the safe browsing blocking page.
+  UMA_HISTOGRAM_ENUMERATION("SafeBrowsing.BlockingPage.ResourceType",
+                            unsafe_resource.resource_type);
   const UnsafeResourceList unsafe_resources{unsafe_resource};
   AwBrowserContext* browser_context =
       AwBrowserContext::FromWebContents(web_contents);

weblayer/browser/safe_browsing/safe_browsing_blocking_page.cc

@@ -4,6 +4,7 @@
 
 #include "weblayer/browser/safe_browsing/safe_browsing_blocking_page.h"
 
+#include "base/metrics/histogram_macros.h"
 #include "components/security_interstitials/content/security_interstitial_controller_client.h"
 #include "components/security_interstitials/content/settings_page_helper.h"
 #include "components/security_interstitials/content/unsafe_resource_util.h"
@@ -35,11 +36,15 @@ SafeBrowsingBlockingPage::SafeBrowsingBlockingPage(
                        std::move(controller_client),
                        display_options) {}
 
+// static
 SafeBrowsingBlockingPage* SafeBrowsingBlockingPage::CreateBlockingPage(
     SafeBrowsingUIManager* ui_manager,
     content::WebContents* web_contents,
     const GURL& main_frame_url,
     const UnsafeResource& unsafe_resource) {
+  // Log the resource type that triggers the safe browsing blocking page.
+  UMA_HISTOGRAM_ENUMERATION("SafeBrowsing.BlockingPage.ResourceType",
+                            unsafe_resource.resource_type);
   const UnsafeResourceList unsafe_resources{unsafe_resource};
   content::NavigationEntry* entry =
       security_interstitials::GetNavigationEntryForResource(unsafe_resource);