Import Traceline, a Windows performance trace event logger.

tools/traceline/traceline/README

Index: tools/traceline/traceline/README
diff --git a/tools/traceline/traceline/README b/tools/traceline/traceline/README
new file mode 100644
index 0000000000000000000000000000000000000000..97ceec8b664f4590749f5adf279be29d739cf694
--- /dev/null
+++ b/tools/traceline/traceline/README
@@ -0,0 +1,21 @@
+Traceline is a Windows utility to intercept, time, and log system calls.  This
+is achieved by injecting code into a target process, along with dynamically
+generated assembly hook stubs.  One of the major goals was to skew performance
+timings as little as possible.  This lead to a design in which the log buffer
+(which is called the playground) is kept within the process, and the logger
+routines use atomic instructions to log their events to this buffer.  At the
+end of the processes lifetime, this buffer is pulled out of the process and
+used to generated JSON output.  In addition to hooking system call activity,
+other hooks of interest have been written, including heap allocation functions.
+Symbols are supported with a command line flag.  This works by capturing the
+process shutdown, and doing an intrusive symbol attach with dbghelp.dll
+
+NOTES:
+  - You should copy dbghelp.dll from a windbg installation into this directory.
+    The version shipped with Windows is old, and symbol support won't work.
+  - You will need a bit of cygwin if you want to use the Makefile.  Otherwise
+    it is pretty clear how to build the files manually.
+  - The output JSON data will be printed out stdout.  It is likely that you
+    will want to pipe the output of this program into a file.
+
+Dean McNamee <deanm@chromium.org>