Set the default accept header for main resources in RenderFrame

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index cfce1ee9392a594905860c1e3c5027f6c39cb55e..6c41d1ae3485d55de6c98b0d1dfd3e09afdd44a8 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -169,6 +169,11 @@ namespace content {
 
 namespace {
 
+const char kDefaultAcceptHeader[] =
+    "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/"
+    "*;q=0.8";
+const char kAcceptHeader[] = "Accept";
+
 const size_t kExtraCharsBeforeAndAfterSelection = 100;
 
 typedef std::map<int, RenderFrameImpl*> RoutingIDFrameMap;
@@ -2404,6 +2409,15 @@ void RenderFrameImpl::willSendRequest(
     }
   }
 
+  // Add the default accept header for frame request if it has not been set
+  // already.

[ppi, 2014/06/05 15:10:10]

In which circumstances it will be already set?

[clamy, 2014/06/05 15:22:01]

This function is also called on redirects. If the header has been modified after
the default header has been set (which I think is unlikely, but for example
devtools can write special headers), then on a redirect the modification would
be overwritten.

+  if ((request.targetType() == blink::WebURLRequest::TargetIsMainFrame ||
+       request.targetType() == blink::WebURLRequest::TargetIsSubframe) &&
+      request.httpHeaderField(WebString::fromUTF8(kAcceptHeader)).isEmpty()) {
+    request.setHTTPHeaderField(WebString::fromUTF8(kAcceptHeader),
+                               WebString::fromUTF8(kDefaultAcceptHeader));
+  }
+
   // Attach |should_replace_current_entry| state to requests so that, should
   // this navigation later require a request transfer, all state is preserved
   // when it is re-created in the new process.