Revert of Android: Make the spare renderer accessible to all Chrome tabs.

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 a17a3c86ebe7bad36a745e09109e8c09606592ec..b71e2c2d6cef81763a7867617648f20445d9303c 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
@@ -37,6 +37,7 @@
 import org.chromium.chrome.browser.ChromeApplication;
 import org.chromium.chrome.browser.IntentHandler;
 import org.chromium.chrome.browser.WarmupManager;
+import org.chromium.chrome.browser.WebContentsFactory;
 import org.chromium.chrome.browser.device.DeviceClassManager;
 import org.chromium.chrome.browser.init.ChromeBrowserInitializer;
 import org.chromium.chrome.browser.net.spdyproxy.DataReductionProxySettings;
@@ -104,6 +105,7 @@
     private final AtomicBoolean mWarmupHasBeenCalled = new AtomicBoolean();
     private final AtomicBoolean mWarmupHasBeenFinished = new AtomicBoolean();
     private ExternalPrerenderHandler mExternalPrerenderHandler;
+    private WebContents mSpareWebContents;
     // TODO(lizeb): Remove once crbug.com/630303 is fixed.
     private boolean mPageLoadMetricsEnabled;
 
@@ -219,12 +221,19 @@
             public void run() {
                 if (!initialized) initializeBrowser(mApplication);
                 if (mayCreateSpareWebContents && mPrerender == null && !SysUtils.isLowEndDevice()) {
-                    WarmupManager.getInstance().createSpareWebContents();
+                    createSpareWebContents();
                 }
                 mWarmupHasBeenFinished.set(true);
             }
         });
         return true;
+    }
+
+    /** Creates a spare {@link WebContents}, if none exists. */
+    private void createSpareWebContents() {
+        ThreadUtils.assertOnUiThread();
+        if (mSpareWebContents != null) return;
+        mSpareWebContents = WebContentsFactory.createWebContentsWithWarmRenderer(false, false);
     }
 
     /** @return the URL converted to string, or null if it's invalid. */
@@ -261,7 +270,7 @@
             didStartPrerender = prerenderUrl(session, url, extras, uid);
         }
         preconnectUrls(otherLikelyBundles);
-        if (!didStartPrerender) WarmupManager.getInstance().createSpareWebContents();
+        if (!didStartPrerender) createSpareWebContents();
     }
 
     /**
@@ -273,7 +282,7 @@
     boolean lowConfidenceMayLaunchUrl(List<Bundle> likelyBundles) {
         ThreadUtils.assertOnUiThread();
         if (!preconnectUrls(likelyBundles)) return false;
-        WarmupManager.getInstance().createSpareWebContents();
+        createSpareWebContents();
         return true;
     }
 
@@ -340,6 +349,20 @@
 
     public Bundle extraCommand(String commandName, Bundle args) {
         return null;
+    }
+
+    /** @return a spare WebContents, or null. */
+    WebContents takeSpareWebContents() {
+        ThreadUtils.assertOnUiThread();
+        WebContents result = mSpareWebContents;
+        mSpareWebContents = null;
+        return result;
+    }
+
+    private void destroySpareWebContents() {
+        ThreadUtils.assertOnUiThread();
+        WebContents webContents = takeSpareWebContents();
+        if (webContents != null) webContents.destroy();
     }
 
     public boolean updateVisuals(final CustomTabsSessionToken session, Bundle bundle) {
@@ -721,7 +744,7 @@
         if (throttle && !mClientManager.isPrerenderingAllowed(uid)) return false;
 
         // A prerender will be requested. Time to destroy the spare WebContents.
-        WarmupManager.getInstance().destroySpareWebContents();
+        destroySpareWebContents();
 
         Intent extrasIntent = new Intent();
         if (extras != null) extrasIntent.putExtras(extras);
@@ -745,6 +768,8 @@
         return true;
     }
 
+
+
     @VisibleForTesting
     void resetThrottling(Context context, int uid) {
         mClientManager.resetThrottling(uid);