Add support for response filtering (issue #515).

- Add a new CefRequestHandler::GetResourceResponseFilter method and
  CefResponseFilter class.

patch/patches/net_filter_515.patch

@@ -0,0 +1,60 @@
+diff --git base/network_delegate.h base/network_delegate.h
+index e8d82a3..8b536d7 100644
+--- base/network_delegate.h
++++ base/network_delegate.h
+@@ -35,6 +35,7 @@ namespace net {
+ // of net/base here, because we have a net_base library. Forward declarations
+ // are ok.
+ class CookieOptions;
++class Filter;
+ class HttpRequestHeaders;
+ class HttpResponseHeaders;
+ class ProxyInfo;
+@@ -118,6 +119,13 @@ class NET_EXPORT NetworkDelegate : public base::NonThreadSafe {
+       const GURL& target_url,
+       const GURL& referrer_url) const;
+ 
++  // Optionally add a new filter to the filter list. Returns the first filter in
++  // the list.
++  virtual Filter* SetupFilter(URLRequest* request,
++                              Filter* filter_list) {
++    return filter_list;
++  }
++
+  private:
+   // This is the interface for subclasses of NetworkDelegate to implement. These
+   // member functions will be called by the respective public notification
+diff --git filter/filter.h filter/filter.h
+index 1904a8c..8d5f1ec 100644
+--- filter/filter.h
++++ filter/filter.h
+@@ -57,6 +57,7 @@
+ #include "net/base/net_export.h"
+ #include "net/base/sdch_manager.h"
+ 
++class CefNetworkDelegate;
+ class GURL;
+ 
+ namespace net {
+@@ -231,6 +232,7 @@ class NET_EXPORT_PRIVATE Filter {
+   std::string OrderedFilterList() const;
+ 
+  protected:
++  friend class ::CefNetworkDelegate;
+   friend class GZipUnitTest;
+   friend class SdchFilterChainingTest;
+   FRIEND_TEST_ALL_PREFIXES(FilterTest, ThreeFilterChain);
+diff --git url_request/url_request_job.cc url_request/url_request_job.cc
+index 641c07b..e613c86 100644
+--- url_request/url_request_job.cc
++++ url_request/url_request_job.cc
+@@ -466,6 +466,9 @@ void URLRequestJob::NotifyHeadersComplete() {
+   if (request_->status().is_success())
+     filter_.reset(SetupFilter());
+ 
++  if (network_delegate_)
++    filter_.reset(network_delegate_->SetupFilter(request_, filter_.release()));
++
+   if (!filter_.get()) {
+     std::string content_length;
+     request_->GetResponseHeaderByName("content-length", &content_length);