Add UMA for tracking Mount/Unmount times.

BUG=873903

Change-Id: I61394811e9264a2ea22cedacd7c782bbc4051bf9
Reviewed-on: https://chromium-review.googlesource.com/1233055Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Anand Mistry <amistry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593473}

chromeos/dbus/cros_disks_client.cc

@@ -23,6 +23,7 @@
 #include "base/strings/stringprintf.h"
 #include "base/sys_info.h"
 #include "base/task_runner_util.h"
+#include "base/time/time.h"
 #include "base/values.h"
 #include "chromeos/dbus/fake_cros_disks_client.h"
 #include "dbus/bus.h"
@@ -170,10 +171,10 @@ class CrosDisksClientImpl : public CrosDisksClient {
     std::vector<std::string> options =
         ComposeMountOptions(mount_options, mount_label, access_mode, remount);
     writer.AppendArrayOfStrings(options);
-    proxy_->CallMethod(
-        &method_call, dbus::ObjectProxy::TIMEOUT_USE_DEFAULT,
-        base::BindOnce(&CrosDisksClientImpl::OnVoidMethod,
-                       weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
+    proxy_->CallMethod(&method_call, dbus::ObjectProxy::TIMEOUT_USE_DEFAULT,
+                       base::BindOnce(&CrosDisksClientImpl::OnMount,
+                                      weak_ptr_factory_.GetWeakPtr(),
+                                      std::move(callback), base::Time::Now()));
   }
 
   // CrosDisksClient override.
@@ -190,10 +191,10 @@ class CrosDisksClientImpl : public CrosDisksClient {
       unmount_options.push_back(kLazyUnmountOption);
 
     writer.AppendArrayOfStrings(unmount_options);
-    proxy_->CallMethod(
-        &method_call, dbus::ObjectProxy::TIMEOUT_USE_DEFAULT,
-        base::BindOnce(&CrosDisksClientImpl::OnUnmount,
-                       weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
+    proxy_->CallMethod(&method_call, dbus::ObjectProxy::TIMEOUT_USE_DEFAULT,
+                       base::BindOnce(&CrosDisksClientImpl::OnUnmount,
+                                      weak_ptr_factory_.GetWeakPtr(),
+                                      std::move(callback), base::Time::Now()));
   }
 
   void EnumerateDevices(EnumerateDevicesCallback callback,
@@ -326,10 +327,23 @@ class CrosDisksClientImpl : public CrosDisksClient {
     std::move(callback).Run(response);
   }
 
+  // Handles the result of Mount and calls |callback|.
+  void OnMount(VoidDBusMethodCallback callback,
+               base::Time start_time,
+               dbus::Response* response) {
+    UMA_HISTOGRAM_MEDIUM_TIMES("CrosDisksClient.MountTime",
+                               base::Time::Now() - start_time);
+    std::move(callback).Run(response);
+  }
+
   // Handles the result of Unmount and calls |callback| or |error_callback|.
-  void OnUnmount(UnmountCallback callback, dbus::Response* response) {
-    const char kUnmountHistogramName[] = "CrosDisksClient.UnmountError";
+  void OnUnmount(UnmountCallback callback,
+                 base::Time start_time,
+                 dbus::Response* response) {
+    UMA_HISTOGRAM_MEDIUM_TIMES("CrosDisksClient.UnmountTime",
+                               base::Time::Now() - start_time);
 
+    const char kUnmountHistogramName[] = "CrosDisksClient.UnmountError";
     if (!response) {
       UMA_HISTOGRAM_ENUMERATION(kUnmountHistogramName, MOUNT_ERROR_UNKNOWN,
                                 MOUNT_ERROR_COUNT);

tools/metrics/histograms/histograms.xml

@@ -15654,6 +15654,13 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="CrosDisksClient.MountTime" units="ms">
+  <owner>amistry@chromium.org</owner>
+  <summary>
+    Time taken by the Chrome OS cros-disks daemon to perform a Mount operation.
+  </summary>
+</histogram>
+
 <histogram name="CrosDisksClient.UnmountError" enum="CrosDisksClientMountError">
   <owner>amistry@chromium.org</owner>
   <summary>
@@ -15662,6 +15669,14 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="CrosDisksClient.UnmountTime" units="ms">
+  <owner>amistry@chromium.org</owner>
+  <summary>
+    Time taken by the Chrome OS cros-disks daemon to perform an Unmount
+    operation.
+  </summary>
+</histogram>
+
 <histogram name="CrosFirstRun.DialogShown">
   <owner>alemate@chromium.org</owner>
   <summary>