Adds Server Previews protocol UMA plus UMA for not accepting previews

components/data_reduction_proxy/core/browser/data_reduction_proxy_network_delegate.cc

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_network_delegate.cc
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_network_delegate.cc b/components/data_reduction_proxy/core/browser/data_reduction_proxy_network_delegate.cc
index 465ec6cf16bb31ab35a54fef218ea4f3707994cb..83584168c9a509e14edc9e11b520895aba64cd2e 100644
--- a/components/data_reduction_proxy/core/browser/data_reduction_proxy_network_delegate.cc
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_network_delegate.cc
@@ -43,6 +43,20 @@ namespace data_reduction_proxy {
 
 namespace {
 
+// Values of the UMA DataReductionProxy.Protocol.AcceptTransform histogram
+// defined in metrics/histograms/histograms.xml. This enum must remain
+// synchronized with DataReductionProxyProtocolAcceptTransformEvent in
+// tools/metrics/histograms/enums.xml.
+enum AcceptTransformEvent {
+  ACCEPT_LITE_PAGE_SENT = 0,

[bengr, 2017/06/28 16:45:50]

How about:

enum AcceptTransformEvent {
  LITE_PAGE_REQUESTED,
  LITE_PAGE_RECEIVED,
  EMPTY_IMAGE_POLICY_RECEIVED,
  EMPTY_IMAGE_REQUESTED,
  EMPTY_IMAGE_RECEIVED,
  VIDEO_REQUESTED,
  ...

[dougarnett, 2017/06/28 22:12:38]

Done.

+  TRANSFORM_LITE_PAGE_RECEIVED = 1,
+  POLICY_EMPTY_IMAGE_RECEIVED = 2,
+  ACCEPT_EMPTY_IMAGE_SENT = 3,
+  TRANSFORM_EMPTY_IMAGE_RECEIVED = 4,
+  ACCEPT_COMPRESSED_VIDEO_SENT = 5,

[bengr, 2017/06/28 16:45:50]

Why no VIDEO_RECEIVED?

[dougarnett, 2017/06/28 22:12:38]

Because it is a 302 redirect to the compressed video rather than CPCT.
[Btw, I'd rather drop recording this SENT value than try to capture that 302 in
the scope of this CL.]

+  ACCEPT_TRANSFORM_EVENT_BOUNDARY
+};
+
 // Records the occurrence of |sample| in |name| histogram. UMA macros are not
 // used because the |name| is not static.
 void RecordNewContentLengthHistogram(const std::string& name, int64_t sample) {
@@ -165,6 +179,53 @@ void RecordContentLengthHistograms(bool lofi_low_header_added,
                           received_content_length);
 }
 
+void RecordAcceptTransformEvent(AcceptTransformEvent event) {
+  UMA_HISTOGRAM_ENUMERATION("DataReductionProxy.Protocol.AcceptTransform",
+                            event, ACCEPT_TRANSFORM_EVENT_BOUNDARY);
+}
+
+void RecordAcceptTransformSentUMA(
+    const net::HttpRequestHeaders& request_headers) {
+  switch (ParseRequestTransform(request_headers)) {
+    case TRANSFORM_LITE_PAGE:
+      RecordAcceptTransformEvent(ACCEPT_LITE_PAGE_SENT);
+      break;
+    case TRANSFORM_EMPTY_IMAGE:
+      RecordAcceptTransformEvent(ACCEPT_EMPTY_IMAGE_SENT);
+      break;
+    case TRANSFORM_COMPRESS_VIDEO:
+      RecordAcceptTransformEvent(ACCEPT_COMPRESSED_VIDEO_SENT);
+      break;
+    case TRANSFORM_NONE:
+      break;
+    case TRANSFORM_PAGE_POLICIES_EMPTY_IMAGE:
+      NOTREACHED();
+      break;
+  }
+}
+
+void RecordAcceptTransformReceivedUMA(const net::URLRequest& request) {
+  net::HttpResponseHeaders* response_headers = request.response_headers();
+  if (response_headers) {

[bengr, 2017/06/28 16:45:50]

I prefer the style:

if (!response_headers)
  return;

switch (...) {
  ...

[dougarnett, 2017/06/28 22:12:38]

Done.

+    switch (ParseResponseTransform(*response_headers)) {
+      case TRANSFORM_LITE_PAGE:
+        RecordAcceptTransformEvent(TRANSFORM_LITE_PAGE_RECEIVED);
+        break;
+      case TRANSFORM_PAGE_POLICIES_EMPTY_IMAGE:
+        RecordAcceptTransformEvent(POLICY_EMPTY_IMAGE_RECEIVED);
+        break;
+      case TRANSFORM_EMPTY_IMAGE:
+        RecordAcceptTransformEvent(TRANSFORM_EMPTY_IMAGE_RECEIVED);
+        break;
+      case TRANSFORM_NONE:
+        break;
+      case TRANSFORM_COMPRESS_VIDEO:
+        NOTREACHED();
+        break;
+    }
+  }
+}
+
 // Verifies that the chrome proxy related request headers are set correctly.
 // |via_chrome_proxy| is true if the request is being fetched via Chrome Data
 // Saver proxy.
@@ -373,6 +434,7 @@ void DataReductionProxyNetworkDelegate::OnBeforeSendHeadersInternal(
   data_reduction_proxy_request_options_->AddRequestHeader(headers, page_id);
 
   VerifyHttpRequestHeaders(true, *headers);
+  RecordAcceptTransformSentUMA(*headers);
 }
 
 void DataReductionProxyNetworkDelegate::OnBeforeRedirectInternal(
@@ -456,6 +518,7 @@ void DataReductionProxyNetworkDelegate::OnCompletedInternal(
   CalculateAndRecordDataUsage(*request, request_type);
 
   RecordContentLength(*request, request_type, original_content_length);
+  RecordAcceptTransformReceivedUMA(*request);
 }
 
 void DataReductionProxyNetworkDelegate::OnHeadersReceivedInternal(