Make tracing work on Android

services/tracing/tracing.mojom

Index: services/tracing/tracing.mojom
diff --git a/services/tracing/tracing.mojom b/services/tracing/tracing.mojom
index e1d0ca0e2a2a076bc1f19fc6b8e111ba40115989..1227988238f8eeb61aeecb97795984a96b73ddeb 100644
--- a/services/tracing/tracing.mojom
+++ b/services/tracing/tracing.mojom
@@ -22,9 +22,9 @@ interface TraceDataCollector {
 };
 
 interface TraceCoordinator {
-  // Request tracing data from all connected TraceControllers to save in a file
-  // derived from |base_name|.
-  Start(string base_name, string categories);
+  // Request tracing data from all connected TraceControllers to stream to
+  // |stream|.
+  Start(handle<data_pipe_producer> stream, string categories);
 
   // Stop tracing and flush results to file.
   StopAndFlush();