[ios] Added web// public API to let embedder observe loading progress.

ios/web/web_state/web_state_delegate_stub.mm

Index: ios/web/web_state/web_state_delegate_stub.mm
diff --git a/ios/web/web_state/web_state_delegate_stub.mm b/ios/web/web_state/web_state_delegate_stub.mm
new file mode 100644
index 0000000000000000000000000000000000000000..78a438ce0ceb46b95470aa245af5de06752e6fdd
--- /dev/null
+++ b/ios/web/web_state/web_state_delegate_stub.mm
@@ -0,0 +1,19 @@
+// 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.
+
+#import "ios/web/web_state/web_state_delegate_stub.h"
+
+#import "ios/web/public/web_state/web_state.h"
+
+@implementation CRWWebStateDelegateStub
+
+@synthesize webState = _webState;
+@synthesize changedProgress = _changedProgress;
+
+- (void)webState:(web::WebState*)webState didChangeProgress:(double)progress {
+  _webState = webState;
+  _changedProgress = progress;
+}
+
+@end