first pass histogram shrink

base/metrics/histogram.h

Index: base/metrics/histogram.h
diff --git a/base/metrics/histogram.h b/base/metrics/histogram.h
index 7a6c6885e5ecb74b54c753b5e31a2f7bb2716f3e..e3ac09ec5d052f979ee09c7685c2be5ada5d3e69 100644
--- a/base/metrics/histogram.h
+++ b/base/metrics/histogram.h
@@ -135,6 +135,25 @@ class Lock;
   } while (0);
 */
 
+#define SMALL_STATIC_HISTOGRAM_POINTER_BLOCK(constant_histogram_name, \
+  histogram_add_method_invocation, \
+  histogram_factory_get_name, \
+                                             ...) \
+  do { \
+    static base::subtle::AtomicWord atomic_histogram_pointer = 0; \
+    base::HistogramBase* histogram_pointer( \
+        reinterpret_cast<base::HistogramBase*>( \
+            base::subtle::Acquire_Load(&atomic_histogram_pointer))); \
+    if (!histogram_pointer) { \
+      histogram_pointer = \
+          histogram_factory_get_name##AndAtomicRelease(&atomic_histogram_pointer, \
+                                                       __VA_ARGS__); \
+    } \
+    DCHECK_EQ(histogram_pointer->histogram_name(), \
+              std::string(constant_histogram_name));    \
+    histogram_pointer->histogram_add_method_invocation; \
+  } while (0)
+
 // The above pattern is repeated in several macros.  The only elements that
 // vary are the invocation of the Add(sample) vs AddTime(sample), and the choice
 // of which FactoryGet method to use.  The different FactoryGet methods have
@@ -152,7 +171,7 @@ class Lock;
             base::subtle::Acquire_Load(&atomic_histogram_pointer))); \
     if (!histogram_pointer) { \
       histogram_pointer = histogram_factory_get_invocation; \
-      base::subtle::Release_Store(&atomic_histogram_pointer, \
+      base::subtle::NoBarrier_Store(&atomic_histogram_pointer, \
           reinterpret_cast<base::subtle::AtomicWord>(histogram_pointer)); \
     } \
     DCHECK_EQ(histogram_pointer->histogram_name(), \
@@ -171,10 +190,17 @@ class Lock;
 
 // For folks that need real specific times, use this to select a precise range
 // of times you want plotted, and the number of buckets you want used.
-#define HISTOGRAM_CUSTOM_TIMES(name, sample, min, max, bucket_count) \
-    STATIC_HISTOGRAM_POINTER_BLOCK(name, AddTime(sample), \
+#if 1
+#define HISTOGRAM_CUSTOM_TIMES(name, sample, min, max, bucket_count)  \
+    STATIC_HISTOGRAM_POINTER_BLOCK(name, AddTime(sample),             \
         base::Histogram::FactoryTimeGet(name, min, max, bucket_count, \
                                         base::HistogramBase::kNoFlags))
+#else
+#define HISTOGRAM_CUSTOM_TIMES(name, sample, min, max, bucket_count) \
+    SMALL_STATIC_HISTOGRAM_POINTER_BLOCK( \
+        name, AddTime(sample), base::Histogram::FactoryTimeGet, \
+        name, min, max, bucket_count, base::HistogramBase::kNoFlags)
+#endif
 
 #define HISTOGRAM_COUNTS(name, sample) HISTOGRAM_CUSTOM_COUNTS( \
     name, sample, 1, 1000000, 50)
@@ -407,6 +433,13 @@ class BASE_EXPORT Histogram : public HistogramBase {
                                        base::TimeDelta maximum,
                                        size_t bucket_count,
                                        int32 flags);
+  static HistogramBase* FactoryTimeGetAndAtomicRelease(
+      base::subtle::AtomicWord* atomic_histogram_pointer,
+      const std::string& name,
+      base::TimeDelta minimum,
+      base::TimeDelta maximum,
+      size_t bucket_count,
+      int32 flags);
 
   // Time call for use with DHISTOGRAM*.
   // Returns TimeTicks::Now() in debug and TimeTicks() in release build.