Add number of CPU cores to UMA logs.

BUG=463922

Review URL: https://codereview.chromium.org/981363002

Cr-Commit-Position: refs/heads/master@{#320009}

components/metrics/metrics_log.cc

@@ -358,6 +358,7 @@ void MetricsLog::RecordEnvironment(
   SystemProfileProto::Hardware::CPU* cpu = hardware->mutable_cpu();
   cpu->set_vendor_name(cpu_info.vendor_name());
   cpu->set_signature(cpu_info.signature());
+  cpu->set_num_cores(base::SysInfo::NumberOfProcessors());
 
   std::vector<ActiveGroupId> field_trial_ids;
   GetFieldTrialIds(&field_trial_ids);

components/metrics/metrics_log_unittest.cc

@@ -127,6 +127,7 @@ class MetricsLogTest : public testing::Test {
     EXPECT_TRUE(hardware.has_cpu());
     EXPECT_TRUE(hardware.cpu().has_vendor_name());
     EXPECT_TRUE(hardware.cpu().has_signature());
+    EXPECT_TRUE(hardware.cpu().has_num_cores());
 
     // TODO(isherman): Verify other data written into the protobuf as a result
     // of this call.

components/metrics/proto/system_profile.proto

@@ -137,6 +137,9 @@ message SystemProfileProto {
 
       // The signature reported by CPUID (from EAX).
       optional uint32 signature = 2;
+
+      // Number of logical processors/cores on the current machine.
+      optional uint32 num_cores = 3;
     }
     optional CPU cpu = 13;