[memory-infra] Add API to ProcessMemoryDump to create ownership edges for base::SharedMemory

base/trace_event/memory_allocator_dump_guid.cc

Index: base/trace_event/memory_allocator_dump_guid.cc
diff --git a/base/trace_event/memory_allocator_dump_guid.cc b/base/trace_event/memory_allocator_dump_guid.cc
index bf4389a4c759f5ae29bc6fda2cb8c4b4cc536871..d1e5c7d5f3141cc63df2ea01287fb6edcedfe53e 100644
--- a/base/trace_event/memory_allocator_dump_guid.cc
+++ b/base/trace_event/memory_allocator_dump_guid.cc
@@ -12,14 +12,32 @@ namespace base {
 namespace trace_event {
 
 namespace {
+
+bool g_use_shared_memory_guid_for_testing = false;
+
 uint64_t HashString(const std::string& str) {
   uint64_t hash[(kSHA1Length + sizeof(uint64_t) - 1) / sizeof(uint64_t)] = {0};
   SHA1HashBytes(reinterpret_cast<const unsigned char*>(str.data()), str.size(),
                 reinterpret_cast<unsigned char*>(hash));
   return hash[0];
 }
+
 }  // namespace
 
+// static
+bool MemoryAllocatorDumpGuid::UseSharedMemoryBasedGUIDs() {
+  // TODO(hajimehoshi): This should just become the default behavior once the
+  // Mojo GUID (crbug.com/604726) is fixed.
+  if (g_use_shared_memory_guid_for_testing)

[Primiano Tucci (use gerrit), 2017/06/08 15:09:33]

I think the global var should just be g_use_shred_mem_guid and only the setter
should be called ForTesting.
Realistically I think that this function here will give you a presubmit warning.

[ssid, 2017/06/08 18:44:23]

Ah yes, presubmit didn't complain for some reason!

+    return true;
+  return false;
+}
+
+// static
+void MemoryAllocatorDumpGuid::SetUseSharedMemoryBasedGUIDsForTesting() {
+  g_use_shared_memory_guid_for_testing = true;
+}
+
 MemoryAllocatorDumpGuid::MemoryAllocatorDumpGuid(uint64_t guid) : guid_(guid) {}
 
 MemoryAllocatorDumpGuid::MemoryAllocatorDumpGuid()