Create a skeleton AppBannerManager class

chrome/android/java/src/org/chromium/chrome/browser/banners/AppBannerManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/banners/AppBannerManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/banners/AppBannerManager.java b/chrome/android/java/src/org/chromium/chrome/browser/banners/AppBannerManager.java
new file mode 100644
index 0000000000000000000000000000000000000000..4aa92215949f79398de65bd075f83915976c7a9d
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/banners/AppBannerManager.java
@@ -0,0 +1,90 @@
+// Copyright 2014 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.banners;
+
+import org.chromium.chrome.browser.EmptyTabObserver;
+import org.chromium.chrome.browser.TabBase;
+import org.chromium.chrome.browser.TabObserver;
+import org.chromium.content.browser.ContentView;
+import org.chromium.content_public.browser.WebContents;
+
+/**
+ * Manages an AppBannerView for a TabBase and its ContentView.
+ *
+ * The AppBannerManager manages a single AppBannerView, dismissing it when the user navigates to a
+ * new page or creating a new one when it detects that the current webpage is requesting a banner
+ * to be built.  The actual observeration of the WebContents (which triggers the automatic creation
+ * and removal of banners, among other things) is done by the native-side AppBannerManager.
+ *
+ * This Java-side class owns its native-side counterpart.
+ */
+public class AppBannerManager {
+    /** Pointer to the native side AppBannerManager. */
+    private final long mNativePointer;
+
+    /** TabBase that the AppBannerView/AppBannerManager is owned by. */
+    private final TabBase mTabBase;
+
+    /** ContentView that the AppBannerView/AppBannerManager is currently attached to. */
+    private ContentView mContentView;
+
+    /**
+     * Constructs an AppBannerManager for the given tab.
+     * @param tab Tab that the AppBannerManager will be attached to.
+     */
+    public AppBannerManager(TabBase tab) {
+        mNativePointer = nativeInit();
+        mTabBase = tab;
+        mTabBase.addObserver(createTabObserver());
+        updatePointers();
+    }
+
+    /**
+     * Creates a TabObserver for monitoring a TabBase, used to react to changes in the ContentView
+     * or to trigger its own destruction.
+     * @return TabObserver that can be used to monitor a TabBase.
+     */
+    private TabObserver createTabObserver() {
+        return new EmptyTabObserver() {
+            @Override
+            public void onWebContentsSwapped(TabBase tab, boolean didStartLoad,
+                    boolean didFinishLoad) {
+                updatePointers();
+            }
+
+            @Override
+            public void onContentChanged(TabBase tab) {
+                updatePointers();
+            }
+
+            @Override
+            public void onDestroyed(TabBase tab) {
+                nativeDestroy(mNativePointer);
+            }
+        };
+    }
+
+    /**
+     * Updates which ContentView and WebContents the AppBannerView is monitoring.
+     */
+    private void updatePointers() {
+        if (mContentView != mTabBase.getContentView()) mContentView = mTabBase.getContentView();
+        nativeReplaceWebContents(mNativePointer, mTabBase.getWebContents());
+    }
+
+    /**
+     * Checks if app banners are enabled.
+     * @return True if banners are enabled, false otherwise.
+     */
+    public static boolean isEnabled() {
+        return nativeIsEnabled();
+    }
+
+    private static native boolean nativeIsEnabled();
+    private native long nativeInit();
+    private native void nativeDestroy(long nativeAppBannerManager);
+    private native void nativeReplaceWebContents(
+            long nativeAppBannerManager, WebContents webContents);
+}