android_webview: stop leaking Contexts.

android_webview/glue/java/src/com/android/webview/chromium/ResourcesContextWrapperFactory.java

 // 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 com.android.webview.chromium;
 
 import android.content.ComponentCallbacks;
 import android.content.Context;
 import android.content.ContextWrapper;
 import android.view.LayoutInflater;
 
-import java.util.WeakHashMap;
-
 /**
  * This class allows us to wrap the application context so that the WebView implementation can
  * correctly reference both org.chromium.* and application classes which is necessary to properly
- * inflate UI.  We keep a weak map from contexts to wrapped contexts to avoid constantly re-wrapping
- * or doubly wrapping contexts.
+ * inflate UI.
  */
 public class ResourcesContextWrapperFactory {
-    private static WeakHashMap<Context, ContextWrapper> sCtxToWrapper =
-            new WeakHashMap<Context, ContextWrapper>();
-    private static final Object sLock = new Object();
-
     private ResourcesContextWrapperFactory() {}
 
     public static Context get(Context ctx) {
-        ContextWrapper wrappedCtx;
-        synchronized (sLock) {
-            wrappedCtx = sCtxToWrapper.get(ctx);
-            if (wrappedCtx == null) {
-                wrappedCtx = createWrapper(ctx);
-                sCtxToWrapper.put(ctx, wrappedCtx);
+        // Avoid double-wrapping a context.
+        if (ctx instanceof WebViewContextWrapper) {
+            return ctx;
+        }
+        return new WebViewContextWrapper(ctx);
+    }
+
+    private static class WebViewContextWrapper extends ContextWrapper {
+        private Context mApplicationContext;
+
+        public WebViewContextWrapper(Context base) {
+            super(base);
+        }
+
+        @Override
+        public ClassLoader getClassLoader() {
+            final ClassLoader appCl = getBaseContext().getClassLoader();
+            final ClassLoader webViewCl = this.getClass().getClassLoader();
+            return new ClassLoader() {
+                @Override
+                protected Class<?> findClass(String name) throws ClassNotFoundException {
+                    // First look in the WebViewProvider class loader.
+                    try {
+                        return webViewCl.loadClass(name);
+                    } catch (ClassNotFoundException e) {
+                        // Look in the app class loader; allowing it to throw
+                        // ClassNotFoundException.
+                        return appCl.loadClass(name);
+                    }
+                }
+            };
+        }
+
+        @Override
+        public Object getSystemService(String name) {
+            if (Context.LAYOUT_INFLATER_SERVICE.equals(name)) {
+                LayoutInflater i = (LayoutInflater) getBaseContext().getSystemService(name);
+                return i.cloneInContext(this);
+            } else {
+                return getBaseContext().getSystemService(name);
             }
         }
-        return wrappedCtx;
-    }
 
-    private static ContextWrapper createWrapper(final Context ctx) {
-        return new ContextWrapper(ctx) {
-            private Context mApplicationContext;
-
-            @Override
-            public ClassLoader getClassLoader() {
-                final ClassLoader appCl = getBaseContext().getClassLoader();
-                final ClassLoader webViewCl = this.getClass().getClassLoader();
-                return new ClassLoader() {
-                    @Override
-                    protected Class<?> findClass(String name) throws ClassNotFoundException {
-                        // First look in the WebViewProvider class loader.
-                        try {
-                            return webViewCl.loadClass(name);
-                        } catch (ClassNotFoundException e) {
-                            // Look in the app class loader; allowing it to throw
-                            // ClassNotFoundException.
-                            return appCl.loadClass(name);
-                        }
-                    }
-                };
-            }
-
-            @Override
-            public Object getSystemService(String name) {
-                if (Context.LAYOUT_INFLATER_SERVICE.equals(name)) {
-                    LayoutInflater i = (LayoutInflater) getBaseContext().getSystemService(name);
-                    return i.cloneInContext(this);
+        @Override
+        public Context getApplicationContext() {
+            if (mApplicationContext == null) {
+                Context appCtx = getBaseContext().getApplicationContext();
+                if (appCtx == getBaseContext()) {
+                    mApplicationContext = this;
                 } else {
-                    return getBaseContext().getSystemService(name);
+                    mApplicationContext = get(appCtx);
                 }
             }
+            return mApplicationContext;
+        }
 
-            @Override
-            public Context getApplicationContext() {
-                if (mApplicationContext == null)
-                    mApplicationContext = get(ctx.getApplicationContext());
-                return mApplicationContext;
-            }
+        @Override
+        public void registerComponentCallbacks(ComponentCallbacks callback) {
+            // We have to override registerComponentCallbacks and unregisterComponentCallbacks
+            // since they call getApplicationContext().[un]registerComponentCallbacks()
+            // which causes us to go into a loop.
+            getBaseContext().registerComponentCallbacks(callback);
+        }
 
-            @Override
-            public void registerComponentCallbacks(ComponentCallbacks callback) {
-                // We have to override registerComponentCallbacks and unregisterComponentCallbacks
-                // since they call getApplicationContext().[un]registerComponentCallbacks()
-                // which causes us to go into a loop.
-                ctx.registerComponentCallbacks(callback);
-            }
-
-            @Override
-            public void unregisterComponentCallbacks(ComponentCallbacks callback) {
-                ctx.unregisterComponentCallbacks(callback);
-            }
-        };
+        @Override
+        public void unregisterComponentCallbacks(ComponentCallbacks callback) {
+            getBaseContext().unregisterComponentCallbacks(callback);
+        }
     }
 }