customtabs: Add a flag to mayLaunchUrl() to force prefetch.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabsConnection.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabsConnection.java b/chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabsConnection.java
index f2f39fb49b0eba90b2c5c08507bc2bd95bcd8cab..f9b9575588c4665d5590b25bf9d4029bc9bcf505 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabsConnection.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabsConnection.java
@@ -72,33 +72,53 @@ public class CustomTabsConnection {
 
     @VisibleForTesting
     static final String PAGE_LOAD_METRICS_CALLBACK = "NavigationMetrics";
+
+    // For testing only, DO NOT USE.
+    @VisibleForTesting
+    static final String DEBUG_OVERRIDE_KEY =
+            "android.support.customtabs.maylaunchurl.DEBUG_OVERRIDE";
+    @VisibleForTesting
+    static final int NO_PRERENDERING = 1;
     @VisibleForTesting
-    static final String NO_PRERENDERING_KEY =
-            "android.support.customtabs.maylaunchurl.NO_PRERENDERING";
+    static final int PREFETCH_ONLY = 2;
 
-    private static AtomicReference<CustomTabsConnection> sInstance =
-            new AtomicReference<CustomTabsConnection>();
+    private static AtomicReference<CustomTabsConnection> sInstance = new AtomicReference<>();
 
+    /** Holds the parameters for the current speculation. */
     @VisibleForTesting
-    static final class PrerenderedUrlParams {
-        public final CustomTabsSessionToken mSession;
-        public final WebContents mWebContents;
-        public final String mUrl;
-        public final String mReferrer;
-        public final Bundle mExtras;
-
-        PrerenderedUrlParams(CustomTabsSessionToken session, WebContents webContents,
-                String url, String referrer, Bundle extras) {
-            mSession = session;
-            mWebContents = webContents;
-            mUrl = url;
-            mReferrer = referrer;
-            mExtras = extras;
+    static final class SpeculationParams {
+        public final CustomTabsSessionToken session;
+        public final String url;
+
+        // Only for prerender.
+        public final WebContents webContents;
+        public final String referrer;
+        public final Bundle extras;
+
+        public final boolean prefetchOnly;
+
+        static SpeculationParams forPrerender(CustomTabsSessionToken session, String url,
+                WebContents webcontents, String referrer, Bundle extras) {
+            return new SpeculationParams(session, url, webcontents, referrer, extras, false);
+        }
+
+        static SpeculationParams forPrefetch(CustomTabsSessionToken session, String url) {
+            return new SpeculationParams(session, url, null, null, null, true);
+        }
+
+        private SpeculationParams(CustomTabsSessionToken session, String url,
+                WebContents webContents, String referrer, Bundle extras, boolean prefetchOnly) {
+            this.session = session;
+            this.url = url;
+            this.webContents = webContents;
+            this.referrer = referrer;
+            this.extras = extras;
+            this.prefetchOnly = prefetchOnly;
         }
     }
 
     @VisibleForTesting
-    PrerenderedUrlParams mPrerender;
+    SpeculationParams mSpeculation;
     protected final Application mApplication;
     protected final ClientManager mClientManager;
     private final boolean mLogRequests;
@@ -217,7 +237,8 @@ public class CustomTabsConnection {
             @Override
             public void run() {
                 if (!initialized) initializeBrowser(mApplication);
-                if (mayCreateSpareWebContents && mPrerender == null && !SysUtils.isLowEndDevice()) {
+                if (mayCreateSpareWebContents && mSpeculation == null
+                        && !SysUtils.isLowEndDevice()) {
                     WarmupManager.getInstance().createSpareWebContents();
                 }
                 mWarmupHasBeenFinished.set(true);
@@ -250,17 +271,26 @@ public class CustomTabsConnection {
             cancelPrerender(session);
             return;
         }
+
+        WarmupManager warmupManager = WarmupManager.getInstance();
+        Profile profile = Profile.getLastUsedProfile();
+
         url = DataReductionProxySettings.getInstance().maybeRewriteWebliteUrl(url);
-        boolean noPrerendering =
-                extras != null ? extras.getBoolean(NO_PRERENDERING_KEY, false) : false;
-        WarmupManager.getInstance().maybePreconnectUrlAndSubResources(
-                Profile.getLastUsedProfile(), url);
-        boolean didStartPrerender = false;
-        if (!noPrerendering && mayPrerender(session)) {
-            didStartPrerender = prerenderUrl(session, url, extras, uid);
+        int debugOverrideValue = extras != null ? extras.getInt(DEBUG_OVERRIDE_KEY, -1) : -1;

[pasko, 2016/10/12 14:18:15]

nit: -1 seems there for consistency with parsing extras in general, but it is
slightly weird to have something like:

-1: no override
0: unused
1: disable prerendering
2: override prerendering with prefetch

[Benoit L, 2016/10/12 15:25:12]

Per offline discussion, let's leave it as is.

+
+        boolean didStartPrerender = false, didStartPrefetch = false;
+        boolean mayPrerender = mayPrerender(session);
+        if (mayPrerender) {
+            if (debugOverrideValue == PREFETCH_ONLY) {

[pasko, 2016/10/12 14:18:15]

nit: a better name would probably be
s/PREFETCH_ONLY/OVERRIDE_PRERENDER_WITH_PREFETCH/ (or something of that sort),
since "only" does not mean it is the only speculation, we'd still preconnect for
low confidence stuff.

really a nit, feel free to leave it as it is, if feels overly verbose

[Benoit L, 2016/10/12 15:25:12]

Acknowledged.

+                didStartPrefetch = new ResourcePrefetchPredictor(profile).startPrefetching(url);
+                if (didStartPrefetch) mSpeculation = SpeculationParams.forPrefetch(session, url);
+            } else if (debugOverrideValue != NO_PRERENDERING) {
+                didStartPrerender = prerenderUrl(session, url, extras, uid);
+            }
         }
         preconnectUrls(otherLikelyBundles);
-        if (!didStartPrerender) WarmupManager.getInstance().createSpareWebContents();
+        if (!didStartPrefetch) warmupManager.maybePreconnectUrlAndSubResources(profile, url);
+        if (!didStartPrerender) warmupManager.createSpareWebContents();
     }
 
     /**
@@ -429,12 +459,20 @@ public class CustomTabsConnection {
      */
     WebContents takePrerenderedUrl(CustomTabsSessionToken session, String url, String referrer) {
         ThreadUtils.assertOnUiThread();
-        if (mPrerender == null || session == null || !session.equals(mPrerender.mSession)) {
+        if (mSpeculation == null || session == null || !session.equals(mSpeculation.session)) {
             return null;
         }
-        WebContents webContents = mPrerender.mWebContents;
-        String prerenderedUrl = mPrerender.mUrl;
-        String prerenderReferrer = mPrerender.mReferrer;
+
+        if (mSpeculation.prefetchOnly) {
+            Profile profile = Profile.getLastUsedProfile();
+            new ResourcePrefetchPredictor(profile).stopPrefetching(mSpeculation.url);
+            mSpeculation = null;
+            return null;
+        }
+
+        WebContents webContents = mSpeculation.webContents;
+        String prerenderedUrl = mSpeculation.url;
+        String prerenderReferrer = mSpeculation.referrer;
         if (referrer == null) referrer = "";
         boolean ignoreFragments = mClientManager.getIgnoreFragmentsForSession(session);
         boolean urlsMatch = TextUtils.equals(prerenderedUrl, url)
@@ -443,7 +481,7 @@ public class CustomTabsConnection {
         WebContents result = null;
         if (urlsMatch && TextUtils.equals(prerenderReferrer, referrer)) {
             result = webContents;
-            mPrerender = null;
+            mSpeculation = null;
         } else {
             cancelPrerender(session);
         }
@@ -457,10 +495,10 @@ public class CustomTabsConnection {
 
     /** Returns the URL prerendered for a session, or null. */
     String getPrerenderedUrl(CustomTabsSessionToken session) {
-        if (mPrerender == null || session == null || !session.equals(mPrerender.mSession)) {
+        if (mSpeculation == null || session == null || !session.equals(mSpeculation.session)) {
             return null;
         }
-        return mPrerender.mUrl;
+        return mSpeculation.webContents != null ? mSpeculation.url : null;
     }
 
     /** See {@link ClientManager#getReferrerForSession(CustomTabsSessionToken)} */
@@ -712,10 +750,11 @@ public class CustomTabsConnection {
     /** Cancels a prerender for a given session, or any session if null. */
     void cancelPrerender(CustomTabsSessionToken session) {
         ThreadUtils.assertOnUiThread();
-        if (mPrerender != null && (session == null || session.equals(mPrerender.mSession))) {
+        if (mSpeculation != null && (session == null || session.equals(mSpeculation.session))
+                && mSpeculation.webContents != null) {
             mExternalPrerenderHandler.cancelCurrentPrerender();
-            mPrerender.mWebContents.destroy();
-            mPrerender = null;
+            mSpeculation.webContents.destroy();
+            mSpeculation = null;
         }
     }
 
@@ -762,7 +801,7 @@ public class CustomTabsConnection {
                 shouldPrerenderOnCellularForSession(session));
         if (webContents == null) return false;
         if (throttle) mClientManager.registerPrerenderRequest(uid, url);
-        mPrerender = new PrerenderedUrlParams(session, webContents, url, referrer, extras);
+        mSpeculation = SpeculationParams.forPrerender(session, url, webContents, referrer, extras);
 
         RecordHistogram.recordBooleanHistogram("CustomTabs.PrerenderSessionUsesDefaultParameters",
                 mClientManager.usesDefaultSessionParameters(session));