Add trace event Pepper API

ppapi/api/dev/ppb_trace_event_dev.idl

+/* Copyright (c) 2012 The Chromium Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/**
+ * This file defines the <code>PPB_Trace_Event</code> interface. It is meant
+ * to be used in plugins as the API that trace macros from trace_event.h use.
+ */
+
+label Chrome {
+  M25 = 0.1
+};
+
+interface PPB_Trace_Event_Dev {
+  /**
+   * Gets a pointer to a character for identifying a category name in the
+   * tracing system as well as for being able to early exit in client-side
+   * tracing code.
+   *
+   * NB: This mem_t return value should technically be const, but return values
+   * for Pepper IDL of mem_t type are not const.  The same is true for the arg
+   * |category_enabled| for AddTraceEvent.
+   */
+  mem_t GetCategoryEnabled([in] cstr_t category_name);
+
+  /**
+   * Adds a trace event to the platform tracing system.

[brettw, 2012/12/19 22:29:25]

Can this be documented more fully? These API files should be as well-defined as
possible, and not require looking at e.g. base to see what everything means.

[elijahtaylor1, 2012/12/21 00:59:16]

Done.

I would like to include a copy of trace_event.h, etc. that will work out of the
box in the C++ pepper library, but would prefer to do that in another change
because it's not exactly pertinent to getting the interface in, and that change
will live more in the NaCl SDK.

+   */
+  int32_t AddTraceEvent(
+      [in] int8_t phase,
+      [in] mem_t category_enabled,
+      [in] cstr_t name,
+      [in] uint64_t id,
+      [in] uint32_t num_args,
+      [in, size_as=num_args] str_t[] arg_names,
+      [in, size_as=num_args] uint8_t[] arg_types,
+      [in, size_as=num_args] uint64_t[] arg_values,
+      [in] int32_t threshold_begin_id,
+      [in] int64_t threshold,
+      [in] uint8_t flags);
+
+  /**
+   * Sets the thread name so it will show up properly in chrome://tracing.

[brettw, 2012/12/19 22:29:25]

Can you put "calling thread" or something in here to specify which thread is
being set?

[elijahtaylor1, 2012/12/21 00:59:16]

Done.

+   */
+  void SetThreadName([in] cstr_t thread_name);
+};