Added more details to failures of memory_test on the GPU bots.

content/test/gpu/gpu_tests/memory.py

Index: content/test/gpu/gpu_tests/memory.py
diff --git a/content/test/gpu/gpu_tests/memory.py b/content/test/gpu/gpu_tests/memory.py
index b56f7375eaa3cdd043d963f90652751139d0dac4..3e1c73be7e3a0e853090faea2e1fc07c7b63164c 100644
--- a/content/test/gpu/gpu_tests/memory.py
+++ b/content/test/gpu/gpu_tests/memory.py
@@ -63,10 +63,10 @@ class _MemoryValidator(page_test.PageTest):
         mb_used = counter.samples[-1] / 1048576
 
     if mb_used + WIGGLE_ROOM_MB < SINGLE_TAB_LIMIT_MB:
-      raise page_test.Failure('Memory allocation too low')
+      raise page_test.Failure(self._FormatException('low', mb_used))
 
     if mb_used - WIGGLE_ROOM_MB > MEMORY_LIMIT_MB:
-      raise page_test.Failure('Memory allocation too high')
+      raise page_test.Failure(self._FormatException('high', mb_used))
 
   def CustomizeBrowserOptions(self, options):
     options.AppendExtraBrowserArgs('--enable-logging')
@@ -77,6 +77,10 @@ class _MemoryValidator(page_test.PageTest):
     custom_categories = ['webkit.console', 'gpu']
     tab.browser.StartTracing(','.join(custom_categories), 60)
 
+  def _FormatException(self, low_or_high, mb_used):
+    return 'Memory allocation too %s (was %d MB, should be %d MB +/- %d MB)' % (
+      low_or_high, mb_used, SINGLE_TAB_LIMIT_MB, WIGGLE_ROOM_MB)
+
 class Memory(test.Test):
   """Tests GPU memory limits"""
   test = _MemoryValidator