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.
+ * It is not supported in Native Client currently.
+ */
+
+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] PP_Instance instance,

[jbauman, 2012/12/14 00:36:07]

Do we actually need the instance parameters on these? In practice they're not
really necessary for anything, and I guess you could also save on the cost of
entering the instance . I'm not sure how that would match the style of the other
pepper interfaces, though.

[brettw, 2012/12/15 00:35:31]

I think all pepper interfaces need a PP_Instance or a PP_Resource.

Doing a pepper call involves a global lock and some map lookups. If this is too
slow for the API (like this is going to be called a lot on the inner loop), then
we probably need to come up with a less chatty interface (like provide a list of
enabled categories in one call, and a way to periodically provide a batch of
several events to the system, and then have the plugin code do all the low-level
management). What we do here may depend on how you intend this to be used.

[elijahtaylor1, 2012/12/18 20:40:31]

I'm not sure if I understand you Brett.  Why is it that all Pepper calls need an
instance or resource?  In the case of this interface, they don't interact with
any other part of pepper AFAIK, it's just that the code that does the tracing
lives in PPB_Instance_Shared.  PTAL at the revisions I made and tell me if that
is not kosher.


On 2012/12/15 00:35:31, brettw wrote:

+                           [in] cstr_t category_name);
+
+  /**
+   * Adds a trace event to the platform tracing system.
+   */
+  int32_t AddTraceEvent(
+      [in] PP_Instance instance,
+      [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.
+   */
+  void SetThreadName([in] PP_Instance instance, [in] cstr_t thread_name);
+};