tracing: Update buffer usage in tracing notifications periodically.

Also fixes the ordering of entries in the NotificationPreferences.

TBR=twellington@chromium.org

Bug: 898512
Change-Id: I2ad01d04a517100b3b0629c053dcd215cd2f838a
Reviewed-on: https://chromium-review.googlesource.com/c/1346071Reviewed-by: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Commit-Queue: Eric Seckler <eseckler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610056}

chrome/android/java/res/xml/tracing_preferences.xml

@@ -3,22 +3,19 @@
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file. -->
 
-<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
+<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" android:orderingFromXml="true">
     <Preference
         android:fragment="org.chromium.chrome.browser.preferences.developer.TracingCategoriesPreferences"
         android:key="default_categories"
-        android:title="@string/prefs_tracing_default_categories_title"
-        android:order="0"/>
+        android:title="@string/prefs_tracing_default_categories_title"/>
     <Preference
         android:fragment="org.chromium.chrome.browser.preferences.developer.TracingCategoriesPreferences"
         android:key="non_default_categories"
-        android:title="@string/prefs_tracing_non_default_categories_title"
-        android:order="1"/>
+        android:title="@string/prefs_tracing_non_default_categories_title"/>
     <org.chromium.chrome.browser.preferences.ChromeBaseListPreference
         android:key="mode"
         android:title="@string/prefs_tracing_mode_title"
-        android:persistent="false"
-        android:order="2"/>
+        android:persistent="false"/>
     <org.chromium.chrome.browser.preferences.ButtonPreference
         android:key="start_recording"/>
     <org.chromium.chrome.browser.preferences.TextMessagePreference

chrome/android/java/src/org/chromium/chrome/browser/tracing/TracingController.java

@@ -73,6 +73,7 @@ public class TracingController {
 
     // Delete shared trace files after 1 hour.
     private static final long DELETE_AFTER_SHARE_TIMEOUT_MILLIS = 60 * 60 * 1000;
+    private static final long UPDATE_BUFFER_USAGE_INTERVAL_MILLIS = 1000;
 
     private static TracingController sInstance;
 
@@ -220,6 +221,20 @@ public class TracingController {
         }
 
         setState(State.RECORDING);
+        updateBufferUsage();
+    }
+
+    private void updateBufferUsage() {
+        if (mState != State.RECORDING) return;
+
+        mNativeController.getTraceBufferUsage(pair -> {
+            if (mState != State.RECORDING) return;
+
+            TracingNotificationManager.updateTracingActiveNotification(pair.first);
+
+            ThreadUtils.postOnUiThreadDelayed(
+                    () -> { updateBufferUsage(); }, UPDATE_BUFFER_USAGE_INTERVAL_MILLIS);
+        });
     }
 
     /**

chrome/android/java/src/org/chromium/chrome/browser/tracing/TracingNotificationManager.java

@@ -28,6 +28,7 @@ public class TracingNotificationManager {
     private static final int TRACING_NOTIFICATION_ID = 100;
 
     private static NotificationManagerProxy sNotificationManagerOverride;
+    private static ChromeNotificationBuilder sTracingActiveNotificationBuilder;
 
     // TODO(eseckler): Consider recording UMAs, see e.g. IncognitoNotificationManager.
 
@@ -85,12 +86,11 @@ public class TracingNotificationManager {
     public static void showTracingActiveNotification() {
         Context context = ContextUtils.getApplicationContext();
         String title = context.getResources().getString(R.string.tracing_active_notification_title);
-        // TODO(eseckler): Update the buffer usage in the notification periodically.
         int bufferUsagePercentage = 0;
         String message = context.getResources().getString(
                 R.string.tracing_active_notification_message, bufferUsagePercentage);
 
-        ChromeNotificationBuilder builder =
+        sTracingActiveNotificationBuilder =
                 createNotificationBuilder()
                         .setContentTitle(title)
                         .setContentText(message)
@@ -99,7 +99,25 @@ public class TracingNotificationManager {
                                 ContextUtils.getApplicationContext().getResources().getString(
                                         R.string.tracing_stop),
                                 TracingNotificationService.getStopRecordingIntent(context));
-        showNotification(builder.build());
+        showNotification(sTracingActiveNotificationBuilder.build());
+    }
+
+    /**
+     * Update the tracing notification that is shown while a trace is being recorded with the
+     * current buffer utilization. Should only be called while the "tracing active" notification is
+     * shown.
+     *
+     * @param bufferUsagePercentage buffer utilization as float between 0 and 1.
+     */
+    public static void updateTracingActiveNotification(float bufferUsagePercentage) {
+        assert (sTracingActiveNotificationBuilder != null);
+        Context context = ContextUtils.getApplicationContext();
+        String message =
+                context.getResources().getString(R.string.tracing_active_notification_message,
+                        Math.round(bufferUsagePercentage * 100));
+
+        sTracingActiveNotificationBuilder.setContentText(message);
+        showNotification(sTracingActiveNotificationBuilder.build());
     }
 
     /**
@@ -149,6 +167,7 @@ public class TracingNotificationManager {
         NotificationManagerProxy manager =
                 getNotificationManager(ContextUtils.getApplicationContext());
         manager.cancel(TRACING_NOTIFICATION_TAG, TRACING_NOTIFICATION_ID);
+        sTracingActiveNotificationBuilder = null;
     }
 
     private static ChromeNotificationBuilder createNotificationBuilder() {