Add ApiActivityMonitor to decouple ActivityLog from low-level extensions code

chrome/browser/extensions/activity_log/counting_policy_unittest.cc

Index: chrome/browser/extensions/activity_log/counting_policy_unittest.cc
diff --git a/chrome/browser/extensions/activity_log/counting_policy_unittest.cc b/chrome/browser/extensions/activity_log/counting_policy_unittest.cc
index 354d0e68c82e8d83d1b1cd56442d35627512cf08..7f66a164c2c251d93893b95902f13cdf6943e051 100644
--- a/chrome/browser/extensions/activity_log/counting_policy_unittest.cc
+++ b/chrome/browser/extensions/activity_log/counting_policy_unittest.cc
@@ -30,6 +30,8 @@
 #include "chrome/browser/chromeos/settings/device_settings_service.h"
 #endif
 
+using content::BrowserThread;
+
 namespace extensions {
 
 class CountingPolicyTest : public testing::Test {
@@ -62,7 +64,7 @@ class CountingPolicyTest : public testing::Test {
   }
 
   // Wait for the task queue for the specified thread to empty.
-  void WaitOnThread(const content::BrowserThread::ID& thread) {
+  void WaitOnThread(const BrowserThread::ID& thread) {
     BrowserThread::PostTaskAndReply(
         thread,
         FROM_HERE,