Perfetto: first commit. Introduce build files

This CL sets up the directory structure, build files and
README for Perfetto. The build files are complete enough
to build a hello-world unittest, gtest, gmock and protobuf
from Linux and Mac OSX without depending on any external
tool. This will allow to build the project without a full
Android checkouot and hence being able to get test coverage
on other waterfalls (Chrome, Travis CI) and with a larger
set of compiler toolchains.
The plan is to generate Android.bp build files in the
next CLs to build the same targets also from the Android tree.

Change-Id: I7a15dcfdb24d5f857fc8c3a70757745741b92545
diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..3f19e61
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1 @@
+BasedOnStyle: Chromium