Add debug exception reporting to GURL#ensureNativeInitializedForGURL

Calls to GURL#ensureNativeInitializedForGURL are much more common than
anticipated (~7% of startups according to UMA), but I'm unable to hit
this during startup locally, so I'd like to collect stacks from Canary
to see where users are hitting this.

Bug: 783819
Change-Id: If9b3681c9b6c786be77c5f1e82c8a7c757fdecf0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2120916Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753329}

chrome/android/java/src/org/chromium/chrome/browser/ChromeApplication.java

@@ -49,7 +49,10 @@ import org.chromium.chrome.browser.vr.OnExitVrRequestListener;
 import org.chromium.chrome.browser.vr.VrModuleProvider;
 import org.chromium.components.embedder_support.application.FontPreloadingWorkaround;
 import org.chromium.components.module_installer.util.ModuleUtil;
+import org.chromium.components.version_info.Channel;
+import org.chromium.components.version_info.VersionConstants;
 import org.chromium.ui.base.ResourceBundle;
+import org.chromium.url.GURL;
 
 /**
  * Basic application functionality that should be shared among all browser applications that use
@@ -124,6 +127,11 @@ public class ChromeApplication extends Application {
 
             // Set Chrome factory for mapping BackgroundTask classes to TaskIds.
             ChromeBackgroundTaskFactory.setAsDefault();
+
+            if (VersionConstants.CHANNEL == Channel.CANARY) {
+                GURL.setReportDebugThrowableCallback(
+                        PureJavaExceptionReporter::reportJavaException);
+            }
         }
 
         // Write installed modules to crash keys. This needs to be done as early as possible so that
@@ -141,6 +149,7 @@ public class ChromeApplication extends Application {
                         PureJavaExceptionReporter::reportJavaException);
             }
         }
+
         AsyncTask.takeOverAndroidThreadPool();
         JNIUtils.setClassLoader(getClassLoader());
         ResourceBundle.setAvailablePakLocales(

url/android/java/src/org/chromium/url/GURL.java

@@ -16,6 +16,10 @@ import org.chromium.base.annotations.MainDex;
 import org.chromium.base.annotations.NativeMethods;
 import org.chromium.base.library_loader.LibraryLoader;
 import org.chromium.base.metrics.RecordHistogram;
+import org.chromium.base.task.PostTask;
+import org.chromium.base.task.TaskTraits;
+
+import java.util.Random;
 
 /**
  * A Java wrapper for GURL, Chromium's URL parsing library.
@@ -35,6 +39,15 @@ public class GURL {
     /* package */ static final int SERIALIZER_VERSION = 1;
     /* package */ static final char SERIALIZER_DELIMITER = '\0';
 
+    @FunctionalInterface
+    public interface ReportDebugThrowableCallback {
+        void run(Throwable throwable);
+    }
+
+    // Right now this is only collecting reports on Canary which has a relatively small population.
+    private static final int DEBUG_REPORT_PERCENTAGE = 10;
+    private static ReportDebugThrowableCallback sReportCallback;
+
     // TODO(https://crbug.com/1039841): Right now we return a new String with each request for a
     //      GURL component other than the spec itself. Should we cache return Strings (as
     //      WeakReference?) so that callers can share String memory?
@@ -67,6 +80,16 @@ public class GURL {
     @CalledByNative
     protected GURL() {}
 
+    /**
+     * Enables debug stack trace gathering for GURL.
+     *
+     * TODO(https://crbug.com/783819): Remove this when the the fraction of users hitting this
+     * drops.
+     */
+    public static void setReportDebugThrowableCallback(ReportDebugThrowableCallback callback) {
+        sReportCallback = callback;
+    }
+
     /**
      * Ensures that the native library is sufficiently loaded for GURL usage.
      *
@@ -75,6 +98,13 @@ public class GURL {
      */
     public static void ensureNativeInitializedForGURL() {
         if (LibraryLoader.getInstance().isInitialized()) return;
+        if (sReportCallback != null && new Random().nextInt(100) < DEBUG_REPORT_PERCENTAGE) {
+            final Throwable throwable = new Throwable("This is not a crash, please ignore.");
+            // This isn't an assert, because by design this is possible, but this path is getting
+            // hit much more than expected and getting stack traces from the wild will help debug.
+            PostTask.postTask(
+                    TaskTraits.BEST_EFFORT_MAY_BLOCK, () -> { sReportCallback.run(throwable); });
+        }
         long time = SystemClock.elapsedRealtime();
         LibraryLoader.getInstance().ensureMainDexInitialized();
         RecordHistogram.recordTimesHistogram("Startup.Android.GURLEnsureMainDexInitialized",