Sync change log file with trunk.

ChangeLog

-2014-05-09: Sentinel
+2014-05-19: Sentinel
 
         The ChangeLog file is no longer maintained on bleeding_edge. This
         sentinel should stay on top of this list.
 
 
+2014-05-19: Version 3.27.7
+
+        Performance and stability improvements on all platforms.
+
+
+2014-05-19: Version 3.27.6
+
+        Performance and stability improvements on all platforms.
+
+
+2014-05-16: Version 3.27.5
+
+        Performance and stability improvements on all platforms.
+
+
+2014-05-15: Version 3.27.4
+
+        Drop thenable coercion cache (Chromium issue 372788).
+
+        Skip write barriers when updating the weak hash table (Chromium issue
+        359401).
+
+        Performance and stability improvements on all platforms.
+
+
+2014-05-14: Version 3.27.3
+
+        Performance and stability improvements on all platforms.
+
+
+2014-05-13: Version 3.27.2
+
+        Harden %SetIsObserved with RUNTIME_ASSERTs (Chromium issue 371782).
+
+        Drop unused static microtask API.
+
+        Introduce an api to query the microtask autorun state of an isolate.
+
+        Performance and stability improvements on all platforms.
+
+
+2014-05-12: Version 3.27.1
+
+        Object.observe: avoid accessing acceptList properties more than once
+        (issue 3315).
+
+        Array Iterator prototype should not have a constructor (issue 3293).
+
+        Fix typos in unit test for Array.prototype.fill().
+
+        Shorten autogenerated error message for functions only (issue 3019,
+        Chromium issue 331971).
+
+        Reland "Removed default Isolate." (Chromium issue 359977).
+
+        Performance and stability improvements on all platforms.
+
+
 2014-05-09: Version 3.27.0
 
         Unbreak samples and tools.
 
         Performance and stability improvements on all platforms.
 
 
 2014-05-08: Version 3.26.33
 
         Removed default Isolate (Chromium issue 359977).
@@ skipping 7355 matching lines @@
         setting break points in them.
 
 
 2008-07-03: Version 0.1.0
 
         Initial export.
 
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