Add LearningSession to BrowserContext

This CL adds a singleton LearningSession to BrowserContext. This
provides a single location from which to get LearningTaskControllers,
which will allow aggregating observations accross multiple frames.

Bug: 994831
Change-Id: Ibeaf47a09ae7408d0afab9bc113a98e9f1532199
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1758625Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Frank Liberato <liberato@chromium.org>
Commit-Queue: Thomas Guilbert <tguilbert@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688733}

content/browser/browser_context.cc

@@ -60,6 +60,7 @@
 #include "media/base/media_switches.h"
 #include "media/capabilities/in_memory_video_decode_stats_db_impl.h"
 #include "media/capabilities/video_decode_stats_db_impl.h"
+#include "media/learning/impl/learning_session_impl.h"
 #include "media/mojo/services/video_decode_perf_history.h"
 #include "mojo/public/cpp/bindings/remote.h"
 #include "net/cookies/cookie_store.h"
@@ -173,6 +174,7 @@ const char kServiceManagerConnection[] = "service-manager-connection";
 const char kServiceInstanceGroup[] = "service-instance-group";
 const char kStoragePartitionMapKeyName[] = "content_storage_partition_map";
 const char kVideoDecodePerfHistoryId[] = "video-decode-perf-history";
+const char kLearningSession[] = "learning-session";
 
 #if defined(OS_CHROMEOS)
 const char kMountPointsKey[] = "mount_points";
@@ -811,6 +813,24 @@ media::VideoDecodePerfHistory* BrowserContext::GetVideoDecodePerfHistory() {
   return decode_history;
 }
 
+media::learning::LearningSession* BrowserContext::GetLearningSession() {
+  media::learning::LearningSession* learning_session =
+      static_cast<media::learning::LearningSession*>(
+          GetUserData(kLearningSession));
+
+  if (!learning_session) {
+    auto new_learning_session =
+        std::make_unique<media::learning::LearningSessionImpl>(
+            base::SequencedTaskRunnerHandle::Get());
+
+    learning_session = new_learning_session.get();
+
+    SetUserData(kLearningSession, std::move(new_learning_session));
+  }
+
+  return learning_session;
+}
+
 download::InProgressDownloadManager*
 BrowserContext::RetriveInProgressDownloadManager() {
   return nullptr;

content/public/browser/browser_context.h

@@ -55,6 +55,9 @@ class Origin;
 
 namespace media {
 class VideoDecodePerfHistory;
+namespace learning {
+class LearningSession;
+}
 }
 
 namespace storage {
@@ -334,6 +337,14 @@ class CONTENT_EXPORT BrowserContext : public base::SupportsUserData {
   // directly, so privacy is not compromised.
   virtual media::VideoDecodePerfHistory* GetVideoDecodePerfHistory();
 
+  // Returns a LearningSession associated with |this|. Used as the central
+  // source from which to retrieve LearningTaskControllers for media machine
+  // learning.
+  // Exposed here rather than StoragePartition because learnings will cover
+  // general media trends rather than SiteInstance specific behavior. The
+  // learnings are not exposed to the web.
+  virtual media::learning::LearningSession* GetLearningSession();
+
   // Retrieves the InProgressDownloadManager associated with this object if
   // available
   virtual download::InProgressDownloadManager*

media/learning/common/learning_session.h

@@ -10,6 +10,7 @@
 
 #include "base/component_export.h"
 #include "base/macros.h"
+#include "base/supports_user_data.h"
 #include "media/learning/common/labelled_example.h"
 #include "media/learning/common/learning_task.h"
 
@@ -19,10 +20,11 @@ namespace learning {
 class LearningTaskController;
 
 // Interface to provide a Learner given the task name.
-class COMPONENT_EXPORT(LEARNING_COMMON) LearningSession {
+class COMPONENT_EXPORT(LEARNING_COMMON) LearningSession
+    : public base::SupportsUserData::Data {
  public:
   LearningSession();
-  virtual ~LearningSession();
+  ~LearningSession() override;
 
   // Return a LearningTaskController for the given task.
   virtual std::unique_ptr<LearningTaskController> GetController(