tcmalloc_unittest: Don't run Realloc test on low memory devices

base/allocator/tcmalloc_unittest.cc

Index: base/allocator/tcmalloc_unittest.cc
diff --git a/base/allocator/tcmalloc_unittest.cc b/base/allocator/tcmalloc_unittest.cc
index 5313bfdf65270f45db2d98783a3cf34286c06ea6..4066079f5e0b108f5d20b2460d4d422cdb12d0a9 100644
--- a/base/allocator/tcmalloc_unittest.cc
+++ b/base/allocator/tcmalloc_unittest.cc
@@ -8,6 +8,7 @@
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/process/process_metrics.h"
+#include "base/sys_info.h"
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -86,6 +87,11 @@ static void TestCalloc(size_t n, size_t s, bool ok) {
   }
 }
 
+bool IsLowMemoryDevice() {
+  // 256MiB

[Primiano Tucci (use gerrit), 2017/04/04 14:10:51]

this is IMHO redundant given the code below, and just prone to end up out of
sync :)

[bcf, 2017/04/04 18:44:06]

Done.

+  return base::SysInfo::AmountOfPhysicalMemory() <= 256LL * 1024 * 1024;
+}
+
 }  // namespace
 
 TEST(TCMallocTest, Malloc) {
@@ -140,6 +146,9 @@ TEST(TCMallocTest, ReallocSmallDelta) {
 #endif
 
 TEST(TCMallocTest, Realloc) {
+  if (IsLowMemoryDevice())

[Primiano Tucci (use gerrit), 2017/04/04 14:10:51]

to be honest, you could have moved the early return to line 165. the top half is
quite small (NextSize goes up to 130k). the problem should be only the 1<<14
below, which * 8192 ends up using 130 MB.

In any case, can you please add a comment saying:

// The logic below tries to allocate kNumEntries * 9000 ~= 130 MB of memory.
This would cause the test to crash on low memory devices with no VM overcommit
(e.g., chromecast).

[bcf, 2017/04/04 18:44:06]

Done.

+    return;
+
   for (int src_size = 0; src_size >= 0; src_size = NextSize(src_size)) {
     for (int dst_size = 0; dst_size >= 0; dst_size = NextSize(dst_size)) {
       unsigned char* src = reinterpret_cast<unsigned char*>(malloc(src_size));