[telemetry] Add new measurement that counts number of GCs needed to free V8 context.

tools/perf/benchmarks/v8.py

Index: tools/perf/benchmarks/v8.py
diff --git a/tools/perf/benchmarks/v8.py b/tools/perf/benchmarks/v8.py
index 5a7c9c95b6dbbbc5b0e91dd8cd68e0f18b1bdf69..d4003a9e683b56be95dfc2517eefb76035446b92 100644
--- a/tools/perf/benchmarks/v8.py
+++ b/tools/perf/benchmarks/v8.py
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import page_sets
+from measurements import v8_detached_context_age_in_gc
 from measurements import v8_gc_times
 from telemetry import benchmark
 
@@ -42,3 +43,14 @@ class V8KeyMobileSites(benchmark.Benchmark):
   @classmethod
   def Name(cls):
     return 'v8.key_mobile_sites_smooth'
+
+class V8DetachedContextAgeInGC(benchmark.Benchmark):
+  """Measures the number of GCs needed to collect a detached context.
+
+  http://www.chromium.org/developers/design-documents/rendering-benchmarks"""
+  test = v8_detached_context_age_in_gc.V8DetachedContextAgeInGC
+  page_set = page_sets.PageReloadCasesPageSet
+
+  @classmethod
+  def Name(cls):
+    return 'v8.detached_context_age_in_gc'