Expose loading state from Blimp to Tab

blimp/client/core/contents/blimp_contents_impl.cc

Index: blimp/client/core/contents/blimp_contents_impl.cc
diff --git a/blimp/client/core/contents/blimp_contents_impl.cc b/blimp/client/core/contents/blimp_contents_impl.cc
index c7ae2fac04767f2bfb8d9be9509dfd7b4bfb3f0c..58dda849fe7c909ede2e565af5605e18712669a2 100644
--- a/blimp/client/core/contents/blimp_contents_impl.cc
+++ b/blimp/client/core/contents/blimp_contents_impl.cc
@@ -105,6 +105,11 @@ void BlimpContentsImpl::OnNavigationStateChanged() {
                     OnNavigationStateChanged());
 }
 
+void BlimpContentsImpl::OnLoadingStateChanged(bool loading) {
+  FOR_EACH_OBSERVER(BlimpContentsObserver, observers_,
+                    OnLoadingStateChanged(loading));
+}
+
 void BlimpContentsImpl::SetSizeAndScale(const gfx::Size& size,
                                         float device_pixel_ratio) {
   tab_control_feature_->SetSizeAndScale(size, device_pixel_ratio);