Adds Server Previews protocol UMA plus UMA for not accepting previews

components/data_reduction_proxy/core/common/data_reduction_proxy_headers.cc

Index: components/data_reduction_proxy/core/common/data_reduction_proxy_headers.cc
diff --git a/components/data_reduction_proxy/core/common/data_reduction_proxy_headers.cc b/components/data_reduction_proxy/core/common/data_reduction_proxy_headers.cc
index ef1e77faa3d285d7bf8659c86e794643d9dfe712..fe139ab1121e5d3cc1ebfcf990d717e82a748317 100644
--- a/components/data_reduction_proxy/core/common/data_reduction_proxy_headers.cc
+++ b/components/data_reduction_proxy/core/common/data_reduction_proxy_headers.cc
@@ -43,6 +43,7 @@ const char kActionValueDelimiter = '=';
 const char kEmptyImageDirective[] = "empty-image";
 const char kLitePageDirective[] = "lite-page";
 const char kCompressedVideoDirective[] = "compressed-video";
+const char kChromeProxyPagePoliciesDirective[] = "page-policies";
 
 // The legacy Chrome-Proxy response header directive for LoFi images.
 const char kLegacyChromeProxyLoFiResponseDirective[] = "q=low";
@@ -121,6 +122,30 @@ bool HasURLRedirectCycle(const std::vector<GURL>& url_chain) {
                    url_chain.back()) != url_chain.rend();
 }
 
+data_reduction_proxy::TransformDirective ParsePagePolicyDirective(
+    const std::string chrome_proxy_header_value) {
+  for (const auto& directive : base::SplitStringPiece(
+           chrome_proxy_header_value, ",", base::TRIM_WHITESPACE,
+           base::SPLIT_WANT_NONEMPTY)) {
+    if (!base::StartsWith(directive, kChromeProxyPagePoliciesDirective,
+                          base::CompareCase::INSENSITIVE_ASCII)) {
+      continue;
+    }
+
+    // Check policy directive for empty-image entry.
+    base::StringPiece page_policies_value = base::StringPiece(directive).substr(
+        arraysize(kChromeProxyPagePoliciesDirective));
+    for (const auto& policy :
+         base::SplitStringPiece(page_policies_value, "|", base::TRIM_WHITESPACE,
+                                base::SPLIT_WANT_NONEMPTY)) {
+      if (base::LowerCaseEqualsASCII(policy, kEmptyImageDirective)) {
+        return data_reduction_proxy::TRANSFORM_PAGE_POLICIES_EMPTY_IMAGE;
+      }
+    }
+  }
+  return data_reduction_proxy::TRANSFORM_NONE;
+}
+
 }  // namespace
 
 namespace data_reduction_proxy {
@@ -169,6 +194,52 @@ const char* if_heavy_qualifier() {
   return kIfHeavyQualifier;
 }
 
+TransformDirective ParseRequestTransform(
+    const net::HttpRequestHeaders& headers) {
+  std::string accept_transform_value;
+  if (!headers.GetHeader(chrome_proxy_accept_transform_header(),
+                         &accept_transform_value)) {
+    return TRANSFORM_NONE;
+  }
+
+  if (base::LowerCaseEqualsASCII(accept_transform_value,
+                                 lite_page_directive())) {
+    return TRANSFORM_LITE_PAGE;
+  } else if (base::LowerCaseEqualsASCII(accept_transform_value,
+                                        empty_image_directive())) {
+    return TRANSFORM_EMPTY_IMAGE;
+  } else if (base::LowerCaseEqualsASCII(accept_transform_value,
+                                        compressed_video_directive())) {
+    return TRANSFORM_COMPRESSED_VIDEO;
+  } else {
+    return TRANSFORM_NONE;
+  }
+}
+
+TransformDirective ParseResponseTransform(
+    const net::HttpResponseHeaders& headers) {
+  std::string content_transform_value;
+  if (!headers.GetNormalizedHeader(chrome_proxy_content_transform_header(),
+                                   &content_transform_value)) {
+    // No content-transform so check for page-policies in chrome-proxy header.
+    std::string chrome_proxy_header_value;
+    if (headers.GetNormalizedHeader(chrome_proxy_header(),
+                                    &chrome_proxy_header_value)) {
+      return ParsePagePolicyDirective(chrome_proxy_header_value);
+    }
+  } else if (base::LowerCaseEqualsASCII(content_transform_value,
+                                        lite_page_directive())) {
+    return TRANSFORM_LITE_PAGE;
+  } else if (base::LowerCaseEqualsASCII(content_transform_value,
+                                        empty_image_directive())) {
+    return TRANSFORM_EMPTY_IMAGE;
+  } else {
+    NOTREACHED() << "Unexpected content transform header: "
+                 << content_transform_value;
+  }
+  return TRANSFORM_NONE;
+}
+
 bool IsEmptyImagePreview(const net::HttpResponseHeaders& headers) {
   return IsPreviewType(headers, kEmptyImageDirective) ||
          headers.HasHeaderValue(kChromeProxyHeader,