Disable precache on svelte.

Precache was enabled for svelte in http://crrev.com/c8e7c272, when the
experiment was only on dev, in the interest in seeing the maximum percent of
users that we could impact.

There is an unconfirmed possibility that the background service may slow down
phones with low RAM/CPU. Until we verify that it does not, we would like to
avoid launching on svelte devices, in order to eliminate any potential for
harm.

This change re-disables the service on svelte devices, by checking
PrivacyPreferencesManager#shouldPrerender() instead of
PrefServiceBridge#getNetworkPredictionEnabled().

BUG=683259

Review-Url: https://codereview.chromium.org/2642733004
Cr-Commit-Position: refs/heads/master@{#445110}

chrome/android/java/src/org/chromium/chrome/browser/precache/PrecacheLauncher.java

@@ -10,7 +10,7 @@
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.CalledByNative;
-import org.chromium.chrome.browser.preferences.PrefServiceBridge;
+import org.chromium.chrome.browser.preferences.privacy.PrivacyPreferencesManager;
 import org.chromium.chrome.browser.sync.ProfileSyncService;
 
 import java.util.EnumSet;
@@ -46,7 +46,7 @@ public static PrecacheLauncher get() {
      */
     private boolean mCalled;
     private boolean mSyncInitialized;
-    private boolean mNetworkPredictionsAllowed;
+    private boolean mPrerenderEnabled;
     private boolean mShouldRun;
 
     /** Destroy the native PrecacheLauncher, releasing the memory that it was using. */
@@ -115,15 +115,13 @@ private void updateEnabledSync(Context context) {
         // thread.
         ThreadUtils.assertOnUiThread();
 
-        boolean networkPredictionEnabledPref =
-                PrefServiceBridge.getInstance().getNetworkPredictionEnabled();
+        boolean prerenderEnabled = PrivacyPreferencesManager.getInstance().shouldPrerender();
         boolean shouldRun = nativeShouldRun();
 
-        mNetworkPredictionsAllowed = networkPredictionEnabledPref;
+        mPrerenderEnabled = prerenderEnabled;
         mShouldRun = shouldRun;
 
-        PrecacheController.setIsPrecachingEnabled(
-                context, networkPredictionEnabledPref && shouldRun);
+        PrecacheController.setIsPrecachingEnabled(context, prerenderEnabled && shouldRun);
         Log.v(TAG, "updateEnabledSync complete");
     }
 
@@ -181,7 +179,7 @@ public EnumSet<FailureReason> failureReasons() {
         EnumSet<FailureReason> reasons = EnumSet.noneOf(FailureReason.class);
         if (!mCalled) reasons.add(FailureReason.UPDATE_PRECACHING_ENABLED_NEVER_CALLED);
         if (!mSyncInitialized) reasons.add(FailureReason.SYNC_NOT_INITIALIZED);
-        if (!mNetworkPredictionsAllowed) {
+        if (!mPrerenderEnabled) {
             reasons.add(FailureReason.PRERENDER_PRIVACY_PREFERENCE_NOT_ENABLED);
         }
         if (!mShouldRun) reasons.add(FailureReason.NATIVE_SHOULD_RUN_IS_FALSE);

chrome/android/javatests/src/org/chromium/chrome/browser/precache/PrecacheLauncherTest.java

@@ -4,6 +4,8 @@
 
 package org.chromium.chrome.browser.precache;
 
+import static org.chromium.base.test.util.Restriction.RESTRICTION_TYPE_NON_LOW_END_DEVICE;
+
 import android.content.Context;
 import android.support.test.filters.SmallTest;
 
@@ -12,6 +14,8 @@
 import org.chromium.base.ContextUtils;
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.test.util.Feature;
+import org.chromium.base.test.util.Restriction;
+import org.chromium.chrome.browser.preferences.privacy.PrivacyPreferencesManager;
 import org.chromium.chrome.browser.sync.ProfileSyncService;
 import org.chromium.content.browser.test.NativeLibraryTestBase;
 
@@ -108,6 +112,9 @@ public void run() {
                 // on the fly.
                 mSync = new StubProfileSyncService();
                 ProfileSyncService.overrideForTests(mSync);
+                // This is currently the default, but let's verify that, lest it ever change and we
+                // get confusing test failures later.
+                assertTrue(PrivacyPreferencesManager.getInstance().shouldPrerender());
             }
         });
     }
@@ -120,6 +127,7 @@ protected void tearDown() throws Exception {
     }
 
     @SmallTest
+    @Restriction(RESTRICTION_TYPE_NON_LOW_END_DEVICE)
     @Feature({"Precache"})
     public void testUpdateEnabled_SyncNotReady_ThenDisabled() {
         mLauncher.updateEnabled(getTargetContext());
@@ -137,6 +145,7 @@ public void testUpdateEnabled_SyncNotReady_ThenDisabled() {
     }
 
     @SmallTest
+    @Restriction(RESTRICTION_TYPE_NON_LOW_END_DEVICE)
     @Feature({"Precache"})
     public void testUpdateEnabled_SyncNotReady_ThenEnabled() {
         mLauncher.updateEnabled(getTargetContext());
@@ -155,6 +164,7 @@ public void testUpdateEnabled_SyncNotReady_ThenEnabled() {
     }
 
     @SmallTest
+    @Restriction(RESTRICTION_TYPE_NON_LOW_END_DEVICE)
     @Feature({"Precache"})
     public void testUpdateEnabled_Disabled_ThenEnabled() {
         setEngineInitialized(true);
@@ -170,6 +180,7 @@ public void testUpdateEnabled_Disabled_ThenEnabled() {
     }
 
     @SmallTest
+    @Restriction(RESTRICTION_TYPE_NON_LOW_END_DEVICE)
     @Feature({"Precache"})
     public void testUpdateEnabled_Enabled_ThenDisabled() {
         mLauncher.setShouldRun(true);
@@ -186,6 +197,7 @@ public void testUpdateEnabled_Enabled_ThenDisabled() {
     }
 
     @SmallTest
+    @Restriction(RESTRICTION_TYPE_NON_LOW_END_DEVICE)
     @Feature({"Precache"})
     public void testUpdateEnabledNullProfileSyncService() {
         ProfileSyncService.overrideForTests(null);