Add DownloadControllerAndroid public interface for android.

android_webview/native/aw_web_contents_delegate.h

Index: android_webview/native/aw_web_contents_delegate.h
diff --git a/android_webview/native/aw_web_contents_delegate.h b/android_webview/native/aw_web_contents_delegate.h
index 1ce3f311cfa7f9e486994088df8d6cf89d37e419..81ba38a39991ef15d8805f0e4ee9c6b9fe2ba188 100644
--- a/android_webview/native/aw_web_contents_delegate.h
+++ b/android_webview/native/aw_web_contents_delegate.h
@@ -27,6 +27,11 @@ class AwWebContentsDelegate
                          const gfx::Rect& selection_rect,
                          int active_match_ordinal,
                          bool final_update) OVERRIDE;
+  virtual bool CanDownload(content::RenderViewHost* source,
+                           int request_id,
+                           const std::string& request_method) OVERRIDE;
+  virtual void OnStartDownload(content::WebContents* source,
+                               content::DownloadItem* download) OVERRIDE;
 };
 
 }  // namespace android_webview