Add Image#getSize for Android

Summary:
I've implemented the getSize method on Image for Android.

**Test plan (required)**

The result in the UIExample app can be seen here:

![android-getsize](https://cloud.githubusercontent.com/assets/570297/15442613/a29c9178-1ee2-11e6-97df-adc20aad0c32.jpg)
Closes https://github.com/facebook/react-native/pull/7664

Differential Revision: D3331704

fbshipit-source-id: d784c861cbc653cd6b49310f4b5516c6583486ca

Examples/UIExplorer/ImageExample.js

@@ -509,7 +509,6 @@ exports.examples = [
     render: function() {
       return <ImageSizeExample source={fullImage} />;
     },
-    platform: 'ios',
   },
 ];
 

Libraries/Image/Image.android.js

@@ -113,6 +113,21 @@ var Image = React.createClass({
 
   statics: {
     resizeMode: ImageResizeMode,
+
+    getSize(
+      url: string,
+      success: (width: number, height: number) => void,
+      failure: (error: any) => void,
+    ) {
+      return ImageLoader.getSize(url)
+        .then(function(sizes) {
+          success(sizes.width, sizes.height);
+        })
+        .catch(failure || function() {
+          console.warn('Failed to get size for image: ' + url);
+        });
+    },
+
     /**
      * Prefetches a remote image for later use by downloading it to the disk
      * cache

ReactAndroid/src/main/java/com/facebook/react/modules/image/ImageLoaderModule.java

@@ -11,11 +11,16 @@ package com.facebook.react.modules.image;
 
 import android.net.Uri;
 
+import com.facebook.react.bridge.Arguments;
+import com.facebook.react.bridge.Callback;
+import com.facebook.react.bridge.WritableMap;
 import com.facebook.common.executors.CallerThreadExecutor;
+import com.facebook.common.references.CloseableReference;
 import com.facebook.datasource.BaseDataSubscriber;
 import com.facebook.datasource.DataSource;
 import com.facebook.datasource.DataSubscriber;
 import com.facebook.drawee.backends.pipeline.Fresco;
+import com.facebook.imagepipeline.image.CloseableImage;
 import com.facebook.imagepipeline.request.ImageRequest;
 import com.facebook.imagepipeline.request.ImageRequestBuilder;
 import com.facebook.react.bridge.Promise;
@@ -27,6 +32,7 @@ public class ImageLoaderModule extends ReactContextBaseJavaModule {
 
   private static final String ERROR_INVALID_URI = "E_INVALID_URI";
   private static final String ERROR_PREFETCH_FAILURE = "E_PREFETCH_FAILURE";
+  private static final String ERROR_GET_SIZE_FAILURE = "E_GET_SIZE_FAILURE";
 
   private final Object mCallerContext;
 
@@ -45,6 +51,64 @@ public class ImageLoaderModule extends ReactContextBaseJavaModule {
     return "ImageLoader";
   }
 
+  @ReactMethod
+  public void getSize(
+      String uriString,
+      final Promise promise) {
+    if (uriString == null || uriString.isEmpty()) {
+      promise.reject(ERROR_INVALID_URI, "Cannot get the size of an image for an empty URI");
+      return;
+    }
+
+    Uri uri = Uri.parse(uriString);
+    ImageRequest request = ImageRequestBuilder.newBuilderWithSource(uri).build();
+
+    DataSource<CloseableReference<CloseableImage>> dataSource =
+      Fresco.getImagePipeline().fetchDecodedImage(request, mCallerContext);
+
+    DataSubscriber<CloseableReference<CloseableImage>> dataSubscriber =
+      new BaseDataSubscriber<CloseableReference<CloseableImage>>() {
+        @Override
+        protected void onNewResultImpl(
+            DataSource<CloseableReference<CloseableImage>> dataSource) {
+          if (!dataSource.isFinished()) {
+            return;
+          }
+          CloseableReference<CloseableImage> ref = dataSource.getResult();
+          if (ref != null) {
+            try {
+              CloseableImage image = ref.get();
+
+              WritableMap sizes = Arguments.createMap();
+              sizes.putInt("width", image.getWidth());
+              sizes.putInt("height", image.getHeight());
+
+              image.close();
+              promise.resolve(sizes);
+            } catch (Exception e) {
+              promise.reject(ERROR_GET_SIZE_FAILURE, e);
+            } finally {
+              CloseableReference.closeSafely(ref);
+              dataSource.close();
+            }
+          } else {
+            dataSource.close();
+            promise.reject(ERROR_GET_SIZE_FAILURE);
+          }
+        }
+
+        @Override
+        protected void onFailureImpl(DataSource<CloseableReference<CloseableImage>> dataSource) {
+          try {
+            promise.reject(ERROR_GET_SIZE_FAILURE, dataSource.getFailureCause());
+          } finally {
+            dataSource.close();
+          }
+        }
+      };
+    dataSource.subscribe(dataSubscriber, CallerThreadExecutor.getInstance());
+  }
+
   /**
    * Prefetches the given image to the Fresco image disk cache.
    *