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

chrome/android/javatests/src/org/chromium/chrome/browser/WarmupManagerTest.java

Index: chrome/android/javatests/src/org/chromium/chrome/browser/WarmupManagerTest.java
diff --git a/chrome/android/javatests/src/org/chromium/chrome/browser/WarmupManagerTest.java b/chrome/android/javatests/src/org/chromium/chrome/browser/WarmupManagerTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..18ce751e828a2162265a944919b38bd496256cc7
--- /dev/null
+++ b/chrome/android/javatests/src/org/chromium/chrome/browser/WarmupManagerTest.java
@@ -0,0 +1,122 @@
+// Copyright 2016 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;
+
+import static org.chromium.base.test.util.Restriction.RESTRICTION_TYPE_LOW_END_DEVICE;
+import static org.chromium.base.test.util.Restriction.RESTRICTION_TYPE_NON_LOW_END_DEVICE;
+
+import android.test.UiThreadTest;
+import android.test.suitebuilder.annotation.SmallTest;
+
+import org.chromium.base.ThreadUtils;
+import org.chromium.base.test.util.Restriction;
+import org.chromium.content.browser.test.NativeLibraryTestBase;
+import org.chromium.content.browser.test.util.Criteria;
+import org.chromium.content.browser.test.util.CriteriaHelper;
+import org.chromium.content_public.browser.WebContents;
+import org.chromium.content_public.browser.WebContentsObserver;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+
+/** Tests for {@link WarmupManager} */
+public class WarmupManagerTest extends NativeLibraryTestBase {
+    private WarmupManager mWarmupManager;
+
+    @Override
+    protected void setUp() throws Exception {
+        super.setUp();
+        loadNativeLibraryAndInitBrowserProcess();
+        ThreadUtils.runOnUiThreadBlocking(new Runnable() {
+            @Override
+            public void run() {
+                mWarmupManager = WarmupManager.getInstance();
+            }
+        });
+    }
+
+    @Override
+    protected void tearDown() throws Exception {
+        super.tearDown();
+        ThreadUtils.runOnUiThreadBlocking(new Runnable() {
+            @Override
+            public void run() {
+                mWarmupManager.destroySpareWebContents();
+            }
+        });
+    }
+
+    @SmallTest
+    @Restriction(RESTRICTION_TYPE_LOW_END_DEVICE)
+    @UiThreadTest
+    public void testNoSpareRendererOnLowEndDevices() {
+        mWarmupManager.createSpareWebContents();
+        assertFalse(mWarmupManager.hasSpareWebContents());
+    }
+
+    @SmallTest
+    @Restriction(RESTRICTION_TYPE_NON_LOW_END_DEVICE)
+    public void testCreateAndTakeSpareRenderer() throws Exception {
+        final AtomicBoolean isRenderViewReady = new AtomicBoolean();
+        final AtomicReference<WebContents> webContentsReference = new AtomicReference<>();
+
+        ThreadUtils.runOnUiThread(new Runnable() {
+            @Override
+            public void run() {
+                mWarmupManager.createSpareWebContents();
+                assertTrue(mWarmupManager.hasSpareWebContents());
+                WebContents webContents = mWarmupManager.takeSpareWebContents(false, false);
+                assertNotNull(webContents);
+                assertFalse(mWarmupManager.hasSpareWebContents());
+                WebContentsObserver observer = new WebContentsObserver(webContents) {
+                    @Override
+                    public void renderViewReady() {
+                        isRenderViewReady.set(true);
+                    }
+                };
+
+                // This is not racy because {@link WebContentsObserver} methods are called on the UI
+                // thread by posting a task. See {@link RenderViewHostImpl::PostRenderViewReady}.
+                webContents.addObserver(observer);
+                webContentsReference.set(webContents);
+            }
+        });
+        CriteriaHelper.pollUiThread(new Criteria("Spare renderer is not initialized") {
+            @Override
+            public boolean isSatisfied() {
+                return isRenderViewReady.get();
+            }
+        });
+        ThreadUtils.runOnUiThread(new Runnable() {
+            @Override
+            public void run() {
+                webContentsReference.get().destroy();
+            }
+        });
+    }
+
+    /** Tests that taking a spare WebContents makes it unavailable to subsequent callers. */
+    @SmallTest
+    @Restriction(RESTRICTION_TYPE_NON_LOW_END_DEVICE)
+    @UiThreadTest
+    public void testTakeSpareWebContents() throws Exception {
+        mWarmupManager.createSpareWebContents();
+        WebContents webContents = mWarmupManager.takeSpareWebContents(false, false);
+        assertNotNull(webContents);
+        assertFalse(mWarmupManager.hasSpareWebContents());
+        webContents.destroy();
+    }
+
+    @SmallTest
+    @Restriction(RESTRICTION_TYPE_NON_LOW_END_DEVICE)
+    @UiThreadTest
+    public void testTakeSpareWebContentsChecksArguments() throws Exception {
+        mWarmupManager.createSpareWebContents();
+        assertNull(mWarmupManager.takeSpareWebContents(true, false));
+        assertNull(mWarmupManager.takeSpareWebContents(false, true));
+        assertNull(mWarmupManager.takeSpareWebContents(true, true));
+        assertTrue(mWarmupManager.hasSpareWebContents());
+    }
+}