Create and pass shared-histogram-allocator from browser to renderer.

base/metrics/histogram_persistence.cc

Index: base/metrics/histogram_persistence.cc
diff --git a/base/metrics/histogram_persistence.cc b/base/metrics/histogram_persistence.cc
index f18d17528354329cd4995615d2451f6a52c59302..4a6b5dc4caf98957089c7dae5ec38d5340c4e80b 100644
--- a/base/metrics/histogram_persistence.cc
+++ b/base/metrics/histogram_persistence.cc
@@ -7,6 +7,7 @@
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/shared_memory.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/histogram_samples.h"
@@ -189,6 +190,28 @@ void SetPersistentHistogramMemoryAllocator(
   g_allocator = allocator;
 }
 
+SharedPersistentMemoryAllocator* CreateSharedPersistentHistogramMemoryAllocator(
+    size_t size,
+    StringPiece name,
+    uint64_t id) {
+  scoped_ptr<SharedMemory> shm(new SharedMemory());
+  shm->CreateAndMapAnonymous(size);
+  return new SharedPersistentMemoryAllocator(std::move(shm), id, name, false);
+}
+
+SharedPersistentMemoryAllocator* CreateSharedPersistentHistogramMemoryAllocator(
+    size_t size,
+    const SharedMemoryHandle& handle,
+    bool readonly) {
+  scoped_ptr<SharedMemory> shm(new SharedMemory(handle, readonly));
+  if (!shm->Map(size)) {
+    NOTREACHED();
+    return nullptr;
+  }
+  return new SharedPersistentMemoryAllocator(std::move(shm), 0, StringPiece(),
+                                             readonly);
+}
+
 PersistentMemoryAllocator* GetPersistentHistogramMemoryAllocator() {
   return g_allocator;
 }