media: Send chrome-cache: frfr on first request.

This allows flywheel to know when it's safe to switch resources.

BUG=504194

Review-Url: https://codereview.chromium.org/2842763003
Cr-Commit-Position: refs/heads/master@{#471139}

components/data_reduction_proxy/core/browser/data_reduction_proxy_network_delegate.cc

@@ -292,6 +292,8 @@ void DataReductionProxyNetworkDelegate::OnBeforeSendHeadersInternal(
     data = DataReductionProxyData::GetDataAndCreateIfNecessary(request);
     if (data)
       data->set_used_data_reduction_proxy(true);
+
+    headers->RemoveHeader(chrome_proxy_header());
     VerifyHttpRequestHeaders(false, *headers);
     return;
   }
@@ -319,6 +321,7 @@ void DataReductionProxyNetworkDelegate::OnBeforeSendHeadersInternal(
       lofi_decider->RemoveAcceptTransformHeader(headers);
     }
     RemoveChromeProxyECTHeader(headers);
+    headers->RemoveHeader(chrome_proxy_header());
     VerifyHttpRequestHeaders(false, *headers);
     return;
   }

media/blink/multibuffer_data_source.cc

@@ -403,7 +403,7 @@ void MultibufferDataSource::ReadTask() {
     bytes_read =
         static_cast<int>(std::min<int64_t>(available, read_op_->size()));
     bytes_read = reader_->TryRead(read_op_->data(), bytes_read);
-
+    url_data_->AddBytesRead(bytes_read);
     if (bytes_read == 0 && total_bytes_ == kPositionNotSpecified) {
       // We've reached the end of the file and we didn't know the total size
       // before. Update the total size so Read()s past the end of the file will

media/blink/resource_multibuffer_data_provider.cc

@@ -85,6 +85,15 @@ void ResourceMultiBufferDataProvider::Start() {
       WebString::FromUTF8(
           net::HttpByteRange::RightUnbounded(byte_pos()).GetHeaderValue()));
 
+  if (url_data_->length() == kPositionNotSpecified &&
+      url_data_->CachedSize() == 0 && url_data_->BytesReadFromCache() == 0) {
+    // This lets the data reduction proxy know that we don't have anything
+    // previously cached data for this resource. We can only send it if this is
+    // the first request for this resource.
+    request.SetHTTPHeaderField(WebString::FromUTF8("chrome-proxy"),
+                               WebString::FromUTF8("frfr"));
+  }
+
   // We would like to send an if-match header with the request to
   // tell the remote server that we really can't handle files other
   // than the one we already started playing. Unfortunately, doing

media/blink/resource_multibuffer_data_provider_unittest.cc

@@ -54,8 +54,16 @@ const int kHttpPartialContent = 206;
 
 enum NetworkState { NONE, LOADED, LOADING };
 
+static bool got_frfr = false;
+
 // Predicate that tests that request disallows compressed data.
-static bool CorrectAcceptEncoding(const blink::WebURLRequest& request) {
+static bool CorrectAcceptEncodingAndProxy(const blink::WebURLRequest& request) {
+  std::string chrome_proxy =
+      request.HttpHeaderField(WebString::FromUTF8("chrome-proxy")).Utf8();
+  if (chrome_proxy != (got_frfr ? "" : "frfr")) {
+    return false;
+  }
+
   std::string value = request
                           .HttpHeaderField(WebString::FromUTF8(
                               net::HttpRequestHeaders::kAcceptEncoding))
@@ -105,8 +113,10 @@ class ResourceMultiBufferDataProviderTest : public testing::Test {
 
   void Start() {
     InSequence s;
-    EXPECT_CALL(*url_loader_,
-                LoadAsynchronously(Truly(CorrectAcceptEncoding), loader_));
+    got_frfr = false;
+    EXPECT_CALL(
+        *url_loader_,
+        LoadAsynchronously(Truly(CorrectAcceptEncodingAndProxy), loader_));
 
     loader_->Start();
   }

media/blink/url_index.cc

@@ -80,6 +80,7 @@ void UrlData::MergeFrom(const scoped_refptr<UrlData>& other) {
     if (last_modified_.is_null()) {
       last_modified_ = other->last_modified_;
     }
+    bytes_read_from_cache_ += other->bytes_read_from_cache_;
     multibuffer()->MergeFrom(other->multibuffer());
   }
 }

media/blink/url_index.h

@@ -139,6 +139,9 @@ class MEDIA_BLINK_EXPORT UrlData : public base::RefCounted<UrlData> {
   // Accessor
   blink::WebFrame* frame() const { return frame_; }
 
+  void AddBytesRead(int64_t b) { bytes_read_from_cache_ += b; }
+  int64_t BytesReadFromCache() { return bytes_read_from_cache_; }
+
  protected:
   UrlData(const GURL& url,
           CORSMode cors_mode,
@@ -170,6 +173,9 @@ class MEDIA_BLINK_EXPORT UrlData : public base::RefCounted<UrlData> {
   // Length of resource this url points to. (in bytes)
   int64_t length_;
 
+  // Number of bytes read from this resource.
+  int64_t bytes_read_from_cache_ = 0;
+
   // Does the server support ranges?
   bool range_supported_;