Added experimental Share API on Android behind flag.

chrome/android/java/src/org/chromium/chrome/browser/webshare/ShareServiceImpl.java

Index: chrome/android/java/src/org/chromium/chrome/browser/webshare/ShareServiceImpl.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webshare/ShareServiceImpl.java b/chrome/android/java/src/org/chromium/chrome/browser/webshare/ShareServiceImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..20af1ef7b77dfbc5a1044bdd7e123e875348b1b3
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webshare/ShareServiceImpl.java
@@ -0,0 +1,77 @@
+// 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.webshare;
+
+import android.content.Context;
+import android.content.Intent;
+
+import org.chromium.chrome.R;
+import org.chromium.content.browser.ContentViewCore;
+import org.chromium.content_public.browser.WebContents;
+import org.chromium.mojo.system.MojoException;
+import org.chromium.mojom.webshare.ShareService;
+import org.chromium.ui.base.WindowAndroid;
+
+/**
+ * Android implementation of the ShareService service defined in
+ * third_party/WebKit/public/platform/modules/webshare/webshare.mojom.
+ */
+public class ShareServiceImpl implements ShareService {
+    private static final String TAG = "ShareServiceImpl";
+
+    private final WindowAndroid mWindow;
+    private final Context mContext;
+
+    public ShareServiceImpl(WebContents webContents) {
+        // Get the Activity for the web contents, which will be used to send the intent.

[Sam McNally, 2016/07/26 08:21:51]

Is this still accurate?

[Matt Giuca, 2016/07/28 05:58:32]

Done.

+        if (webContents == null) {

[Sam McNally, 2016/07/26 08:21:51]

Please add helper functions to map from WebContents to WindowAndroid and from
WindowAndroid to Context, propagating nulls. This is noisier than it should be.

[Matt Giuca, 2016/07/28 05:58:32]

Done.

+            mWindow = null;
+            mContext = null;
+            return;
+        }
+
+        ContentViewCore contentViewCore = ContentViewCore.fromWebContents(webContents);
+        if (contentViewCore == null) {
+            mWindow = null;
+            mContext = null;
+            return;
+        }
+
+        mWindow = contentViewCore.getWindowAndroid();
+        if (mWindow == null) {
+            mContext = null;
+            return;
+        }
+
+        mContext = mWindow.getActivity().get();
+        if (mContext == null) return;

[Sam McNally, 2016/07/26 08:21:51]

Is this really necessary?

[Matt Giuca, 2016/07/28 05:58:32]

No, it was a joke lol.

+    }
+
+    @Override
+    public void close() {}
+
+    @Override
+    public void onConnectionError(MojoException e) {}
+
+    @Override
+    public void share(String title, String text, ShareResponse callback) {
+        String chooserTitle = mContext.getString(R.string.share_link_chooser_title);
+        Intent send = new Intent(Intent.ACTION_SEND);
+        send.setType("text/plain");
+        send.putExtra(Intent.EXTRA_SUBJECT, text);
+        send.putExtra(Intent.EXTRA_TEXT, text);
+
+        Intent chooser = Intent.createChooser(send, chooserTitle);
+        if (!mWindow.showIntent(chooser, null, null)) {
+            callback.call("Could not start intent");

[Sam McNally, 2016/07/26 08:21:52]

I don't think we should expose platform-specific errors if we can avoid it.

[Matt Giuca, 2016/07/28 05:58:32]

I think we should just return an enum of errors if we can help it; I'll add a
TODO but for now, making the error more vague SGTM.

+            return;
+        }
+
+        // Success.
+        // TODO(mgiuca): Wait until the user has made a choice, and report failure if they cancel
+        // the picker or something else goes wrong.
+        callback.call(null);
+    }
+}