CustomTabs: Base version for prerender switch

chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabsConnection.java

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.customtabs;
 
 import android.app.ActivityManager;
 import android.app.Application;
 import android.app.PendingIntent;
 import android.content.Context;
@@ skipping 71 matching lines @@
     // For testing only, DO NOT USE.
     @VisibleForTesting
     static final String DEBUG_OVERRIDE_KEY =
             "android.support.customtabs.maylaunchurl.DEBUG_OVERRIDE";
     private static final int NO_OVERRIDE = 0;
     @VisibleForTesting
     static final int NO_PRERENDERING = 1;
     @VisibleForTesting
     static final int PREFETCH_ONLY = 2;
 
+    @VisibleForTesting
+    static final String PRERENDER_MODE_KEY = "android.support.customtabs.PRERENDER_MODE";
+    @VisibleForTesting
+    static final int DEFAULT_PRERENDER = 0;

[ahemery, 2017/03/16 17:28:35]

Not sure of the name

+
     private static AtomicReference<CustomTabsConnection> sInstance = new AtomicReference<>();
 
     /** Holds the parameters for the current speculation. */
     @VisibleForTesting
     static final class SpeculationParams {
         public final CustomTabsSessionToken session;
         public final String url;
 
         // Only for prerender.
         public final WebContents webContents;
@@ skipping 17 matching lines @@
             this.url = url;
             this.webContents = webContents;
             this.referrer = referrer;
             this.extras = extras;
             this.prefetchOnly = prefetchOnly;
         }
     }
 
     @VisibleForTesting
     SpeculationParams mSpeculation;
+    @VisibleForTesting
+    int mPrerenderMode;
     protected final Application mApplication;
     protected final ClientManager mClientManager;
     private final boolean mLogRequests;
     private final AtomicBoolean mWarmupHasBeenCalled = new AtomicBoolean();
     private final AtomicBoolean mWarmupHasBeenFinished = new AtomicBoolean();
     private ExternalPrerenderHandler mExternalPrerenderHandler;
     private boolean mForcePrerenderForTesting;
 
     // Conversion between native TimeTicks and SystemClock.uptimeMillis().
     private long mNativeTickOffsetUs;
@@ skipping 187 matching lines @@
         int debugOverrideValue = NO_OVERRIDE;
         if (extras != null) debugOverrideValue = extras.getInt(DEBUG_OVERRIDE_KEY, NO_OVERRIDE);
 
         boolean didStartPrerender = false, didStartPrefetch = false;
         boolean mayPrerender = mayPrerender(session);
         if (mayPrerender) {
             if (debugOverrideValue == PREFETCH_ONLY) {
                 didStartPrefetch = new ResourcePrefetchPredictor(profile).startPrefetching(url);
                 if (didStartPrefetch) mSpeculation = SpeculationParams.forPrefetch(session, url);
             } else if (debugOverrideValue != NO_PRERENDERING) {
-                didStartPrerender = prerenderUrl(session, url, extras, uid);
+                didStartPrerender = startPrerender(session, url, extras, uid);
             }
         }
         preconnectUrls(otherLikelyBundles);
         if (!didStartPrefetch) warmupManager.maybePreconnectUrlAndSubResources(profile, url);
         if (!didStartPrerender) warmupManager.createSpareWebContents();
     }
 
     /**
      * Low confidence mayLaunchUrl() call, that is:
      * - Preconnects to the ordered list of URLs.
@@ skipping 546 matching lines @@
         // connection type as well, we should either change that or add another check for custom
         // tabs. Then PrivacyManager should be used to make the below check.
         if (!PrefServiceBridge.getInstance().getNetworkPredictionEnabled()) return false;
         if (DataReductionProxySettings.getInstance().isDataReductionProxyEnabled()) return false;
         ConnectivityManager cm =
                 (ConnectivityManager) mApplication.getApplicationContext().getSystemService(
                         Context.CONNECTIVITY_SERVICE);
         return !cm.isActiveNetworkMetered() || shouldPrerenderOnCellularForSession(session);
     }
 
+    @VisibleForTesting
+    void cancelPrerender(CustomTabsSessionToken session) {

[ahemery, 2017/03/16 17:28:35]

Generic function to cancel the prerendering of a URL

+        switch (mPrerenderMode) {
+            case DEFAULT_PRERENDER:
+                cancelWebContentsPrerender(session);
+                break;
+            default:
+                return;
+        }
+    }
+
     /** Cancels a prerender for a given session, or any session if null. */
-    void cancelPrerender(CustomTabsSessionToken session) {
+    private void cancelWebContentsPrerender(CustomTabsSessionToken session) {

[ahemery, 2017/03/16 17:28:35]

Version targeting what we know typically as "prerender". Running out of names
here...

         ThreadUtils.assertOnUiThread();
         if (mSpeculation != null && (session == null || session.equals(mSpeculation.session))
                 && mSpeculation.webContents != null) {
             mExternalPrerenderHandler.cancelCurrentPrerender();
             mSpeculation.webContents.destroy();
             mSpeculation = null;
         }
     }
 
+    private boolean startPrerender(

[ahemery, 2017/03/16 17:28:35]

Generic function to start prerendering a URL

+            CustomTabsSessionToken session, String url, Bundle extras, int uid) {
+        // Last one wins and cancels the previous prerender.
+        cancelPrerender(null);
+        switch (mPrerenderMode) {
+            case DEFAULT_PRERENDER:
+                return prerenderUrl(session, url, extras, uid);
+            default:
+                return false;
+        }
+    }
+
     /**
      * Tries to request a prerender for a given URL.
      *
      * @param session Session the request comes from.
      * @param url URL to prerender.
      * @param extras extra parameters.
      * @param uid UID of the caller.
      * @return true if a prerender has been initiated.
      */
     private boolean prerenderUrl(
             CustomTabsSessionToken session, String url, Bundle extras, int uid) {
         ThreadUtils.assertOnUiThread();
-        // Ignores mayPrerender() for an empty URL, since it cancels an existing prerender.

[ahemery, 2017/03/16 17:28:35]

This is already done in maylaunchUrl and it makes more sense to be done there.
Since the function is private, we are sure no other unexpected callers relying
on this behaviour exist.

-        if (!mayPrerender(session) && !TextUtils.isEmpty(url)) return false;
         if (!mWarmupHasBeenCalled.get()) return false;
-        // Last one wins and cancels the previous prerender.
-        cancelPrerender(null);
-        if (TextUtils.isEmpty(url)) return false;
+
         boolean throttle = !shouldPrerenderOnCellularForSession(session);
         if (throttle && !mClientManager.isPrerenderingAllowed(uid)) return false;
 
         // A prerender will be requested. Time to destroy the spare WebContents.
         WarmupManager.getInstance().destroySpareWebContents();
 
         Intent extrasIntent = new Intent();
         if (extras != null) extrasIntent.putExtras(extras);
         if (IntentHandler.getExtraHeadersFromIntent(extrasIntent) != null) return false;
         if (mExternalPrerenderHandler == null) {
             mExternalPrerenderHandler = new ExternalPrerenderHandler();
         }
         Rect contentBounds = ExternalPrerenderHandler.estimateContentSize(mApplication, true);
         String referrer = IntentHandler.getReferrerUrlIncludingExtraHeaders(extrasIntent);
         if (referrer == null && getReferrerForSession(session) != null) {
             referrer = getReferrerForSession(session).getUrl();
         }
         if (referrer == null) referrer = "";
-        Pair<WebContents, WebContents> webContentsPair = mExternalPrerenderHandler.addPrerender(

[ahemery, 2017/03/16 17:28:35]

Auto formatting

-                Profile.getLastUsedProfile(), url, referrer,
-                contentBounds,
-                shouldPrerenderOnCellularForSession(session));
+        Pair<WebContents, WebContents> webContentsPair =
+                mExternalPrerenderHandler.addPrerender(Profile.getLastUsedProfile(), url, referrer,
+                        contentBounds, shouldPrerenderOnCellularForSession(session));
         if (webContentsPair == null) return false;
         WebContents dummyWebContents = webContentsPair.first;
         if (webContentsPair.second != null) {
             mClientManager.resetPostMessageHandlerForSession(session, webContentsPair.second);
         }
         if (throttle) mClientManager.registerPrerenderRequest(uid, url);
-        mSpeculation = SpeculationParams.forPrerender(

[ahemery, 2017/03/16 17:28:35]

Auto formatting

-                session, url, dummyWebContents, referrer, extras);
+        mSpeculation =
+                SpeculationParams.forPrerender(session, url, dummyWebContents, referrer, extras);
 
         RecordHistogram.recordBooleanHistogram("CustomTabs.PrerenderSessionUsesDefaultParameters",
                 mClientManager.usesDefaultSessionParameters(session));
 
         return true;
     }
 
     @VisibleForTesting
     void resetThrottling(Context context, int uid) {
         mClientManager.resetThrottling(uid);
     }
 
     @VisibleForTesting
     void ban(Context context, int uid) {
         mClientManager.ban(uid);
     }
 
     @VisibleForTesting
     void setForcePrerender(boolean force) {
         mForcePrerenderForTesting = force;
     }
+
+    @VisibleForTesting
+    void setPrerenderMode(int mode) {

[ahemery, 2017/03/16 17:28:35]

The new switch that enables toggling between usual prerender and other modes
(e.g. hidden tab). The clear is done to avoid mixed states.

+        if (mPrerenderMode != mode) {
+            // Remove all existing speculations when switching mode
+            cancelPrerender(null);
+            mPrerenderMode = mode;
+        }
+    }
 }