Add the skeleton of a heap profiling component.

The component will contain heap_profiling code that depends on content/, and
needs to be used by Desktop Chrome, Android, and Android Webview.

Bug: 827545
Change-Id: I32e93b800d315c9e99df8cc778bc770c640953ba
Reviewed-on: https://chromium-review.googlesource.com/1005319Reviewed-by: Cait Phillips <caitkp@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549584}

components/heap_profiling/OWNERS

+erikchen@chromium.org

components/heap_profiling/README.md

+The heap profiler records heap allocations, and exports heap dumps via Chrome
+tracing.
+
+The code is divided into three directories:
+
+* components/services/heap_profiling/ contains the core logic that records
+  allocations.
+* components/heap_profiling/ [this directory] contains
+  * Logic that hooks up processes to the heap_profiling service [depends on
+    content/].
+  * End to end tests [depends on content/].
+* chrome/browser/profiling_host/ contains:
+  * Logic that hooks up UI surfaces to the heap_profiling service.
+  * Logic to automatically upload heap dumps in the wild.