metrics: Deprecate "perf_data" in UMA proto

components/metrics/proto/chrome_user_metrics_extension.proto

Index: components/metrics/proto/chrome_user_metrics_extension.proto
diff --git a/components/metrics/proto/chrome_user_metrics_extension.proto b/components/metrics/proto/chrome_user_metrics_extension.proto
index cf52be233a561a1ef2a40fdfe270ed79b2fe3fbf..61abd360906cf107a9485cdee49867b70b730e40 100644
--- a/components/metrics/proto/chrome_user_metrics_extension.proto
+++ b/components/metrics/proto/chrome_user_metrics_extension.proto
@@ -16,7 +16,6 @@ import "omnibox_event.proto";
 import "profiler_event.proto";
 import "system_profile.proto";
 import "user_action_event.proto";
-import "perf_data.proto";
 import "sampled_profile.proto";
 
 // Next tag: 13
@@ -60,9 +59,6 @@ message ChromeUserMetricsExtension {
   repeated HistogramEventProto histogram_event = 6;
   repeated ProfilerEventProto profiler_event = 7;
 
-  // TODO(sque): Deprecate this field and use |sampled_profile| instead.
-  repeated PerfDataProto perf_data = 8;

[Ilya Sherman, 2015/03/26 00:14:05]

To the best of my knowledge, the best practice is to annotate the field as
"[deprecated]", rather than deleting it from the protocol buffer.

[Simon Que, 2015/03/26 00:42:09]

Done.

-
   // A list of all collected sample-based profiles since the last UMA upload.
   repeated SampledProfile sampled_profile = 11;