Enable new ownership edges for base::SharedMemory

Now mojo is fixed to pass unique IDs across processes, Let's enable new
ownership edges for base::SharedMemory and remove old ownership edges.

Perf sheriffs: If you see sharp bumps in metrics like cc/gpu/discardable/
shared_memory this is very likely the culrprit, please revert it.

Bug: 604726
Change-Id: Iad7bf261f3e2c884d60e935cb2635923de46b2e2
Reviewed-on: https://chromium-review.googlesource.com/557741
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Reviewed-by: Siddhartha S <ssid@chromium.org>
Reviewed-by: Primiano Tucci <primiano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488174}

base/trace_event/memory_allocator_dump_guid.cc

@@ -13,7 +13,7 @@ namespace trace_event {
 
 namespace {
 
-bool g_use_shared_memory_guid = false;
+bool g_use_shared_memory_guid = true;
 
 uint64_t HashString(const std::string& str) {
   uint64_t hash[(kSHA1Length + sizeof(uint64_t) - 1) / sizeof(uint64_t)] = {0};
@@ -33,11 +33,6 @@ bool MemoryAllocatorDumpGuid::UseSharedMemoryBasedGUIDs() {
   return false;
 }
 
-// static
-void MemoryAllocatorDumpGuid::SetUseSharedMemoryBasedGUIDsForTesting() {
-  g_use_shared_memory_guid = true;
-}
-
 MemoryAllocatorDumpGuid::MemoryAllocatorDumpGuid(uint64_t guid) : guid_(guid) {}
 
 MemoryAllocatorDumpGuid::MemoryAllocatorDumpGuid()

base/trace_event/memory_allocator_dump_guid.h

@@ -19,7 +19,6 @@ class BASE_EXPORT MemoryAllocatorDumpGuid {
   // If the clients of base::SharedMemory should use the global dump guid(s)
   // created by SharedMemoryTracker.
   static bool UseSharedMemoryBasedGUIDs();
-  static void SetUseSharedMemoryBasedGUIDsForTesting();
 
   MemoryAllocatorDumpGuid();
   explicit MemoryAllocatorDumpGuid(uint64_t guid);

base/trace_event/process_memory_dump_unittest.cc

@@ -332,43 +332,12 @@ TEST(ProcessMemoryDumpTest, GlobalAllocatorDumpTest) {
   ASSERT_EQ(MemoryAllocatorDump::Flags::DEFAULT, shared_mad1->flags());
 }
 
-TEST(ProcessMemoryDumpTest, OldSharedMemoryOwnershipTest) {
+TEST(ProcessMemoryDumpTest, SharedMemoryOwnershipTest) {
   std::unique_ptr<ProcessMemoryDump> pmd(
       new ProcessMemoryDump(nullptr, kDetailedDumpArgs));
   const ProcessMemoryDump::AllocatorDumpEdgesMap& edges =
       pmd->allocator_dumps_edges_for_testing();
 
-  auto* shm_dump1 = pmd->CreateAllocatorDump("shared_mem/seg1");
-
-  auto* client_dump1 = pmd->CreateAllocatorDump("discardable/segment1");
-  MemoryAllocatorDumpGuid client_global_guid1(1);
-  auto shm_token1 = UnguessableToken::Create();
-  MemoryAllocatorDumpGuid shm_global_guid1 =
-      SharedMemoryTracker::GetGlobalDumpIdForTracing(shm_token1);
-  pmd->AddOverridableOwnershipEdge(shm_dump1->guid(), shm_global_guid1,
-                                   0 /* importance */);
-
-  pmd->CreateSharedMemoryOwnershipEdge(client_dump1->guid(),
-                                       client_global_guid1, shm_token1,
-                                       1 /* importance */);
-
-  EXPECT_EQ(2u, edges.size());
-  EXPECT_EQ(shm_global_guid1, edges.find(shm_dump1->guid())->second.target);
-  EXPECT_EQ(0, edges.find(shm_dump1->guid())->second.importance);
-  EXPECT_TRUE(edges.find(shm_dump1->guid())->second.overridable);
-  EXPECT_EQ(client_global_guid1,
-            edges.find(client_dump1->guid())->second.target);
-  EXPECT_EQ(1, edges.find(client_dump1->guid())->second.importance);
-  EXPECT_FALSE(edges.find(client_dump1->guid())->second.overridable);
-}
-
-TEST(ProcessMemoryDumpTest, NewSharedMemoryOwnershipTest) {
-  std::unique_ptr<ProcessMemoryDump> pmd(
-      new ProcessMemoryDump(nullptr, kDetailedDumpArgs));
-  const ProcessMemoryDump::AllocatorDumpEdgesMap& edges =
-      pmd->allocator_dumps_edges_for_testing();
-  MemoryAllocatorDumpGuid::SetUseSharedMemoryBasedGUIDsForTesting();
-
   auto* client_dump2 = pmd->CreateAllocatorDump("discardable/segment2");
   MemoryAllocatorDumpGuid client_global_guid2(2);
   auto shm_token2 = UnguessableToken::Create();