Add UMA to report requests for key systems using RequestMediaKeyAccess

Adding a UMA to keep track of the number of times RequestMediaKeyAccess
is called with a particular key system, and the number of times the
request succeeds. The counts are only incremented once per renderer
frame.

BUG=351501
TEST=existing EME tests pass, verified UMA locally

Review URL: https://codereview.chromium.org/881853002

Cr-Commit-Position: refs/heads/master@{#313956}

media/blink/webencryptedmediaclient_impl.cc

@@ -5,6 +5,7 @@
 #include "webencryptedmediaclient_impl.h"
 
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "media/base/key_systems.h"
@@ -18,6 +19,10 @@
 
 namespace media {
 
+// These names are used by UMA.
+const char kKeySystemSupportUMAPrefix[] =
+    "Media.EME.RequestMediaKeySystemAccess.";
+
 static bool IsSupportedContentType(
     const std::string& key_system,
     const std::string& mime_type,
@@ -131,6 +136,56 @@ static bool GetSupportedConfiguration(
   return true;
 }
 
+// Report usage of key system to UMA. There are 2 different counts logged:
+// 1. The key system is requested.
+// 2. The requested key system and options are supported.
+// Each stat is only reported once per renderer frame per key system.
+// Note that WebEncryptedMediaClientImpl is only created once by each
+// renderer frame.
+class WebEncryptedMediaClientImpl::Reporter {
+ public:
+  enum KeySystemSupportStatus {
+    KEY_SYSTEM_REQUESTED = 0,
+    KEY_SYSTEM_SUPPORTED = 1,
+    KEY_SYSTEM_SUPPORT_STATUS_COUNT
+  };
+
+  explicit Reporter(const std::string& key_system_for_uma)
+      : uma_name_(kKeySystemSupportUMAPrefix + key_system_for_uma),
+        is_request_reported_(false),
+        is_support_reported_(false) {}
+  ~Reporter() {}
+
+  void ReportRequested() {
+    if (is_request_reported_)
+      return;
+    Report(KEY_SYSTEM_REQUESTED);
+    is_request_reported_ = true;
+  }
+
+  void ReportSupported() {
+    DCHECK(is_request_reported_);
+    if (is_support_reported_)
+      return;
+    Report(KEY_SYSTEM_SUPPORTED);
+    is_support_reported_ = true;
+  }
+
+ private:
+  void Report(KeySystemSupportStatus status) {
+    // Not using UMA_HISTOGRAM_ENUMERATION directly because UMA_* macros
+    // require the names to be constant throughout the process' lifetime.
+    base::LinearHistogram::FactoryGet(
+        uma_name_, 1, KEY_SYSTEM_SUPPORT_STATUS_COUNT,
+        KEY_SYSTEM_SUPPORT_STATUS_COUNT + 1,
+        base::Histogram::kUmaTargetedHistogramFlag)->Add(status);
+  }
+
+  const std::string uma_name_;
+  bool is_request_reported_;
+  bool is_support_reported_;
+};
+
 WebEncryptedMediaClientImpl::WebEncryptedMediaClientImpl(
     scoped_ptr<CdmFactory> cdm_factory,
     MediaPermission* /* media_permission */)
@@ -158,6 +213,11 @@ void WebEncryptedMediaClientImpl::requestMediaKeySystemAccess(
   }
 
   std::string key_system = base::UTF16ToASCII(request.keySystem());
+
+  // Report this request to the appropriate Reporter.
+  Reporter* reporter = GetReporter(key_system);
+  reporter->ReportRequested();
+
   if (!IsConcreteSupportedKeySystem(key_system)) {
     request.requestNotSupported("Unsupported keySystem");
     return;
@@ -173,6 +233,7 @@ void WebEncryptedMediaClientImpl::requestMediaKeySystemAccess(
   // TODO(sandersd): Remove once Blink requires the configurations parameter for
   // requestMediaKeySystemAccess().
   if (configurations.isEmpty()) {
+    reporter->ReportSupported();
     request.requestSucceeded(WebContentDecryptionModuleAccessImpl::Create(
         request.keySystem(), blink::WebMediaKeySystemConfiguration(),
         request.securityOrigin(), cdm_factory_.get()));
@@ -185,6 +246,7 @@ void WebEncryptedMediaClientImpl::requestMediaKeySystemAccess(
     if (GetSupportedConfiguration(key_system, candidate,
                                   request.securityOrigin(),
                                   &accumulated_configuration)) {
+      reporter->ReportSupported();
       request.requestSucceeded(WebContentDecryptionModuleAccessImpl::Create(
           request.keySystem(), accumulated_configuration,
           request.securityOrigin(), cdm_factory_.get()));
@@ -197,4 +259,19 @@ void WebEncryptedMediaClientImpl::requestMediaKeySystemAccess(
       "None of the requested configurations were supported.");
 }
 
+// Lazily create Reporters.
+WebEncryptedMediaClientImpl::Reporter* WebEncryptedMediaClientImpl::GetReporter(
+    const std::string& key_system) {
+  std::string uma_name = GetKeySystemNameForUMA(key_system);
+  Reporter* reporter = reporters_.get(uma_name);
+  if (reporter != nullptr)
+    return reporter;
+
+  // Reporter not found, so create one.
+  auto result =
+      reporters_.add(uma_name, make_scoped_ptr(new Reporter(uma_name)));
+  DCHECK(result.second);
+  return result.first->second;
+}
+
 }  // namespace media

media/blink/webencryptedmediaclient_impl.h

@@ -5,6 +5,9 @@
 #ifndef MEDIA_BLINK_WEBENCRYPTEDMEDIACLIENT_IMPL_H_
 #define MEDIA_BLINK_WEBENCRYPTEDMEDIACLIENT_IMPL_H_
 
+#include <string>
+
+#include "base/containers/scoped_ptr_hash_map.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/cdm_factory.h"
 #include "media/base/media_export.h"
@@ -27,6 +30,20 @@ class MEDIA_EXPORT WebEncryptedMediaClientImpl
       blink::WebEncryptedMediaRequest request);
 
  private:
+  // Report usage of key system to UMA. There are 2 different counts logged:
+  // 1. The key system is requested.
+  // 2. The requested key system and options are supported.
+  // Each stat is only reported once per renderer frame per key system.
+  class Reporter;
+
+  // Gets the Reporter for |key_system|. If it doesn't already exist,
+  // create one.
+  Reporter* GetReporter(const std::string& key_system);
+
+  // Key system <-> Reporter map.
+  typedef base::ScopedPtrHashMap<std::string, Reporter> Reporters;
+  Reporters reporters_;
+
   scoped_ptr<CdmFactory> cdm_factory_;
 };
 

tools/metrics/histograms/histograms.xml

@@ -12472,6 +12472,16 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Media.EME.RequestMediaKeySystemAccess"
+    enum="RequestMediaKeySystemAccessStatus">
+  <owner>sandersd@chromium.org</owner>
+  <summary>
+    Key system support query status and result, as reported by
+    RequestMediaKeySystemAccess. Each value will be reported at most once per
+    renderer process.
+  </summary>
+</histogram>
+
 <histogram name="Media.EME.Unknown" enum="CdmPromiseResult">
   <owner>sandersd@chromium.org</owner>
   <summary>
@@ -55777,6 +55787,11 @@ To add a new entry, add it with any value and run test to compute valid value.
   </int>
 </enum>
 
+<enum name="RequestMediaKeySystemAccessStatus" type="int">
+  <int value="0" label="Requested"/>
+  <int value="1" label="Supported"/>
+</enum>
+
 <enum name="ResolutionCategory" type="int">
   <int value="0" label="RESOLVE_SUCCESS"/>
   <int value="1" label="RESOLVE_FAIL"/>
@@ -62746,6 +62761,14 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Event.Latency.RendererImpl"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="RequestMediaKeySystemAccessKeySystems" separator=".">
+  <suffix name="ClearKey" label="Requests for the Clear Key key system."/>
+  <suffix name="Unknown"
+      label="Requests for an unknown or unsupported key system."/>
+  <suffix name="Widevine" label="Requests for the Widevine key system."/>
+  <affected-histogram name="Media.EME.RequestMediaKeySystemAccess"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="ResourcePrefetchPredictorNetworkTypePrefetch"
     separator=".">
   <suffix name="NotPrefetched"