AW: add metric for support library client

No change to logic.

This adds an UMA metric to see if the WebViewClient is a
WebViewClientCompat or not. This will only ever be boolean (at least for
the foreseeable future), so this should be safe to keep as a boolean
histogram for now.

R=changwan@chromium.org, isherman@chromium.org

Bug: 901581
Test: N/A (not feasible to test metrics right now)
Change-Id: I9e6ba219d4f5f26f1fec947ef9974549490e2258
Reviewed-on: https://chromium-review.googlesource.com/c/1318748
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605888}

android_webview/support_library/callback/java/src/org/chromium/support_lib_callback_glue/SupportLibWebViewContentsClientAdapter.java

@@ -14,6 +14,7 @@ import org.chromium.android_webview.AwContentsClient.AwWebResourceError;
 import org.chromium.android_webview.AwSafeBrowsingResponse;
 import org.chromium.android_webview.ScopedSysTraceEvent;
 import org.chromium.base.Callback;
+import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.support_lib_boundary.SafeBrowsingResponseBoundaryInterface;
 import org.chromium.support_lib_boundary.WebResourceErrorBoundaryInterface;
 import org.chromium.support_lib_boundary.WebViewClientBoundaryInterface;
@@ -30,6 +31,9 @@ public class SupportLibWebViewContentsClientAdapter {
     private static final String WEBVIEW_CLIENT_COMPAT_NAME = "androidx.webkit.WebViewClientCompat";
     private static final String[] EMPTY_FEATURE_LIST = new String[0];
 
+    private static final String COMPAT_CLIENT_HISTOGRAM =
+            "Android.WebView.SupportLibrary.ClientIsCompat";
+
     // If {@code null}, this indicates the WebViewClient is not a WebViewClientCompat. Otherwise,
     // this is a Proxy for the WebViewClientCompat.
     @Nullable
@@ -47,6 +51,13 @@ public class SupportLibWebViewContentsClientAdapter {
             mWebViewClientSupportedFeatures = mWebViewClient == null
                     ? EMPTY_FEATURE_LIST
                     : mWebViewClient.getSupportedFeatures();
+
+            // We ignore the case where the client is set to null, since this is often done by
+            // WebView's internal logic (such as during destroy()), and would otherwise skew data.
+            if (possiblyCompatClient != null) {
+                RecordHistogram.recordBooleanHistogram(
+                        COMPAT_CLIENT_HISTOGRAM, mWebViewClient != null);
+            }
         }
     }
 

tools/metrics/histograms/enums.xml

@@ -53076,6 +53076,11 @@ Full version information for the fingerprint enum values:
   <int value="1" label="Revoked ephemeral permission"/>
 </enum>
 
+<enum name="WebViewClientTypeEnum">
+  <int value="0" label="Regular WebViewClient"/>
+  <int value="1" label="WebViewClientCompat (via AndroidX)"/>
+</enum>
+
 <enum name="WelcomeSignInPromptOutcome">
   <int value="0" label="User navigated away from page"/>
   <int value="1" label="User clicked the No Thanks button"/>

tools/metrics/histograms/histograms.xml

@@ -2737,6 +2737,18 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="Android.WebView.SupportLibrary.ClientIsCompat"
+    enum="WebViewClientTypeEnum" expires_after="2019-05-05">
+  <owner>ntfschr@chromium.org</owner>
+  <owner>changwan@chromium.org</owner>
+  <summary>
+    Records whether the WebViewClient provided by the app is an instance of
+    WebViewClientCompat (and therefore exposes AndroidX callbacks). This is
+    recorded each time the app sets a new WebViewClient via
+    WebView#setWebViewClient().
+  </summary>
+</histogram>
+
 <histogram name="Android.WebView.TargetSdkVersion" enum="AndroidApiLevel">
   <owner>changwan@chromium.org</owner>
   <summary>