blink/public: Update some references to WebKit in the README

Point to paths that actually exist after the great Blink mv from a while
ago.

TBR=haraken

Change-Id: I22431a1abdf786ad9fe98188df5002e60733a182
Reviewed-on: https://chromium-review.googlesource.com/c/1355165Reviewed-by: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Commit-Queue: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/master@{#612213}

third_party/blink/public/README.md

@@ -31,13 +31,13 @@ runs. Rather than communicating directly with the underlying operating system,
 Blink is designed to run in a sandbox and interacts with the operating system
 via the platform API. The central interface in this part of the API is
 Platform, which is a pure virtual interface from which Blink obtains many other
-interfaces. public/platform/ is implemented by WebKit/Source/platform/exported/.
+interfaces. public/platform/ is implemented by blink/renderer/platform/exported.
 
 The public/web directory defines an interface to Blink's implementation of the
 web platform, including the Document Object Model (DOM). The central interface
 in this part of the API is WebView, which is a good starting point for
 exploring the API. public/web/ is implemented by
-WebKit/Source/{core,modules,controller}/exported/.
+blink/renderer/{core,modules}/exported/.
 
 Note that public/platform should not depend on public/web.