Add UMA for the size backoff in FilesListRequestRunner.

This CL adds UMA so we can say how much the backoff is used.

TEST=Checked chrome://histograms.
BUG=433716

Review URL: https://codereview.chromium.org/1220023002

Cr-Commit-Position: refs/heads/master@{#336991}

2 files changed, 18 insertions, 9 deletions

diff --git a/google_apis/drive/drive_api_error_codes.h b/google_apis/drive/drive_api_error_codes.h
index 10aa901..62ab938 100644
--- a/google_apis/drive/drive_api_error_codes.h
+++ b/google_apis/drive/drive_api_error_codes.h
@@ -9,7 +9,8 @@
 
 namespace google_apis {
 
-// HTTP errors that can be returned by Drive API service.
+// HTTP errors that can be returned by Drive API service. Keep all the values
+// positive, as they are used for UMA histograms.
 enum DriveApiErrorCode {
   HTTP_SUCCESS               = 200,
   HTTP_CREATED               = 201,
@@ -29,14 +30,15 @@ enum DriveApiErrorCode {
   HTTP_NOT_IMPLEMENTED       = 501,
   HTTP_BAD_GATEWAY           = 502,
   HTTP_SERVICE_UNAVAILABLE   = 503,
-  DRIVE_PARSE_ERROR          = -100,
-  DRIVE_FILE_ERROR           = -101,
-  DRIVE_CANCELLED            = -102,
-  DRIVE_OTHER_ERROR          = -103,
-  DRIVE_NO_CONNECTION        = -104,
-  DRIVE_NOT_READY            = -105,
-  DRIVE_NO_SPACE             = -106,
-  DRIVE_RESPONSE_TOO_LARGE   = -107
+  DRIVE_PARSE_ERROR          = 1000,
+  DRIVE_FILE_ERROR           = 1001,
+  DRIVE_CANCELLED            = 1002,
+  DRIVE_OTHER_ERROR          = 1003,
+  DRIVE_NO_CONNECTION        = 1004,
+  DRIVE_NOT_READY            = 1005,
+  DRIVE_NO_SPACE             = 1006,
+  DRIVE_RESPONSE_TOO_LARGE   = 1007
+  // If modified, update the enum mapping in histograms.xml.
 };
 
 // Returns a string representation of DriveApiErrorCode.
diff --git a/google_apis/drive/files_list_request_runner.cc b/google_apis/drive/files_list_request_runner.cc
index 8bf50be..c3588b7 100644
--- a/google_apis/drive/files_list_request_runner.cc
+++ b/google_apis/drive/files_list_request_runner.cc
@@ -5,6 +5,8 @@
 #include "google_apis/drive/files_list_request_runner.h"
 
 #include "base/bind.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/metrics/sparse_histogram.h"
 #include "google_apis/drive/drive_api_error_codes.h"
 #include "google_apis/drive/drive_api_requests.h"
 #include "google_apis/drive/request_sender.h"
@@ -27,6 +29,8 @@ CancelCallback FilesListRequestRunner::CreateAndStartWithSizeBackoff(
     const std::string& q,
     const std::string& fields,
     const FileListCallback& callback) {
+  UMA_HISTOGRAM_COUNTS_1000("Drive.FilesListRequestRunner.MaxResults",
+                            max_results);
   base::Closure* const cancel_callback = new base::Closure;
   drive::FilesListRequest* const request = new drive::FilesListRequest(
       request_sender_, url_generator_,
@@ -61,6 +65,9 @@ void FilesListRequestRunner::OnCompleted(int max_results,
   if (!request_completed_callback_for_testing_.is_null())
     request_completed_callback_for_testing_.Run();
 
+  UMA_HISTOGRAM_SPARSE_SLOWLY(
+      "Drive.FilesListRequestRunner.ApiErrorCode", error);
+
   if (error == google_apis::DRIVE_RESPONSE_TOO_LARGE && max_results > 1) {
     CreateAndStartWithSizeBackoff(max_results / 2, q, fields, callback);
     return;