Extensions: Add metrics for Web Request API actions.

extensions/browser/api/web_request/web_request_api.cc

Index: extensions/browser/api/web_request/web_request_api.cc
diff --git a/extensions/browser/api/web_request/web_request_api.cc b/extensions/browser/api/web_request/web_request_api.cc
index b81023248535d3064adaf563327f06568d444b64..e6633ce7e6d537f87e9f1ab82a350296ad9dc4dc 100644
--- a/extensions/browser/api/web_request/web_request_api.cc
+++ b/extensions/browser/api/web_request/web_request_api.cc
@@ -87,7 +87,21 @@ namespace web_request = api::web_request;
 
 namespace {
 
+// Describes the action taken by the Web Request API for a given stage of a web
+// request.
+// These values are written to logs.  New enum values can be added, but existing
+// enum values must never be renumbered or deleted and reused.
+enum RequestAction {
+  CANCEL = 0,
+  REDIRECT = 1,
+  MODIFY_REQUEST_HEADERS = 2,
+  MODIFY_RESPONSE_HEADERS = 3,
+  SET_AUTH_CREDENTIALS = 4,
+  MAX
+};
+
 const char kWebRequestEventPrefix[] = "webRequest.";
+const char kWebRequestActionUMA[] = "Extensions.WebRequestAction";
 
 // List of all the webRequest events.
 const char* const kWebRequestEvents[] = {
@@ -1816,18 +1830,26 @@ int ExtensionWebRequestEventRouter::ExecuteDeltas(
         blocked_request.new_url, &warnings, blocked_request.net_log);
   } else if (blocked_request.event == kOnBeforeSendHeaders) {
     CHECK(!blocked_request.callback.is_null());
+    bool request_headers_modified = false;
     helpers::MergeOnBeforeSendHeadersResponses(
-        blocked_request.response_deltas,
-        blocked_request.request_headers,
-        &warnings,
-        blocked_request.net_log);
+        blocked_request.response_deltas, blocked_request.request_headers,
+        &warnings, blocked_request.net_log, &request_headers_modified);
+    if (request_headers_modified)

[Devlin, 2017/02/24 21:43:43]

nit: { } around multi-line if statement bodies.

[karandeepb, 2017/02/25 03:55:19]

Done.

+      UMA_HISTOGRAM_ENUMERATION(kWebRequestActionUMA,
+                                RequestAction::MODIFY_REQUEST_HEADERS,
+                                RequestAction::MAX);
   } else if (blocked_request.event == kOnHeadersReceived) {
     CHECK(!blocked_request.callback.is_null());
+    bool response_headers_modified = false;
     helpers::MergeOnHeadersReceivedResponses(
         blocked_request.request->url(), blocked_request.response_deltas,
         blocked_request.original_response_headers.get(),
         blocked_request.override_response_headers, blocked_request.new_url,
-        &warnings, blocked_request.net_log);
+        &warnings, blocked_request.net_log, &response_headers_modified);
+    if (response_headers_modified)
+      UMA_HISTOGRAM_ENUMERATION(kWebRequestActionUMA,
+                                RequestAction::MODIFY_RESPONSE_HEADERS,
+                                RequestAction::MAX);
   } else if (blocked_request.event == kOnAuthRequired) {
     CHECK(blocked_request.callback.is_null());
     CHECK(!blocked_request.auth_callback.is_null());
@@ -1852,9 +1874,16 @@ int ExtensionWebRequestEventRouter::ExecuteDeltas(
 
   if (canceled) {
     request_time_tracker_->SetRequestCanceled(request_id);
-  } else if (blocked_request.new_url &&
-             !blocked_request.new_url->is_empty()) {
+    UMA_HISTOGRAM_ENUMERATION(kWebRequestActionUMA, RequestAction::CANCEL,
+                              RequestAction::MAX);
+  } else if (blocked_request.new_url && !blocked_request.new_url->is_empty()) {
     request_time_tracker_->SetRequestRedirected(request_id);
+    UMA_HISTOGRAM_ENUMERATION(kWebRequestActionUMA, RequestAction::REDIRECT,
+                              RequestAction::MAX);
+  } else if (credentials_set) {
+    UMA_HISTOGRAM_ENUMERATION(kWebRequestActionUMA,
+                              RequestAction::SET_AUTH_CREDENTIALS,
+                              RequestAction::MAX);
   }
 
   // This triggers onErrorOccurred if canceled is true.