GetAllocatorDump should not return black hold dump

GetAllocatorDump is used to check if dump was created. Do not return
black hole dump from here.

BUG=854668

Change-Id: Ife41be2622e9476d8e45586ace3ea316012341c3
Reviewed-on: https://chromium-review.googlesource.com/1111017
Commit-Queue: Helen Li <xunjieli@chromium.org>
Reviewed-by: Helen Li <xunjieli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569596}

base/trace_event/process_memory_dump.cc

@@ -272,8 +272,6 @@ MemoryAllocatorDump* ProcessMemoryDump::GetAllocatorDump(
   auto it = allocator_dumps_.find(absolute_name);
   if (it != allocator_dumps_.end())
     return it->second.get();
-  if (black_hole_mad_)
-    return black_hole_mad_.get();
   return nullptr;
 }
 

base/trace_event/process_memory_dump_unittest.cc

@@ -386,6 +386,10 @@ TEST(ProcessMemoryDumpTest, BackgroundModeTest) {
   SetAllocatorDumpNameWhitelistForTesting(kTestDumpNameWhitelist);
   MemoryAllocatorDump* black_hole_mad = pmd->GetBlackHoleMad();
 
+  // GetAllocatorDump works for uncreated dumps.
+  EXPECT_EQ(nullptr, pmd->GetAllocatorDump("NotWhitelisted/TestName"));
+  EXPECT_EQ(nullptr, pmd->GetAllocatorDump("Whitelisted/TestName"));
+
   // Invalid dump names.
   EXPECT_EQ(black_hole_mad,
             pmd->CreateAllocatorDump("NotWhitelisted/TestName"));
@@ -419,7 +423,7 @@ TEST(ProcessMemoryDumpTest, BackgroundModeTest) {
             pmd->CreateAllocatorDump("Whitelisted/0xaB/TestName"));
 
   // GetAllocatorDump is consistent.
-  EXPECT_EQ(black_hole_mad, pmd->GetAllocatorDump("NotWhitelisted/TestName"));
+  EXPECT_EQ(nullptr, pmd->GetAllocatorDump("NotWhitelisted/TestName"));
   EXPECT_NE(black_hole_mad, pmd->GetAllocatorDump("Whitelisted/TestName"));
 
   // Test whitelisted entries.