tracing: Add macros for generating context trace events
These macros can be used to annotate sections of code that are working
on specific trace contexts. For example, to mark a piece of code as
belonging to a particular HTML frame:
TRACE_EVENT_ENTER_CONTEXT("blink", "FrameContext", &my_frame);
// Do something with |my_frame|.
TRACE_EVENT_LEAVE_CONTEXT("blink", "FrameContext", &my_frame);
The patch also adds a scoped helper:
TraceScopedContext scoped_context("blink", "FrameContext", &my_frame);
For more details see the design doc:
https://docs.google.com/document/d/15BB-suCb9j-nFt55yCFJBJCGzLg2qUm3WaSOPb8APtI/edit?pli=1#heading=h.4lvgp19u6rwx
BUG=546021
Review URL: https://codereview.chromium.org/1499683002
Cr-Commit-Position: refs/heads/master@{#370976}
CrOS-Libchrome-Original-Commit: 29ffcdce7014502105f8d95a97259c910ba3b8be
3 files changed