Support zero-sized values.

base/debug/activity_tracker.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/debug/activity_tracker.h"
 
 #include <algorithm>
 #include <limits>
 #include <utility>
 
@@ skipping 313 matching lines @@
     // If the value is actually a single byte, see if it can be stuffed at the
     // end of the name extent rather than wasting kMemoryAlignment bytes.
     if (size == 1 && name_extent > name_size) {
       full_size = base_size;
       --name_extent;
       --base_size;
     }
 
     // Truncate the stored size to the amount of available memory. Stop now if
     // there's not any room for even part of the value.
-    size = std::min(full_size - base_size, size);
-    if (size == 0)
-      return;
+    if (size != 0) {
+      size = std::min(full_size - base_size, size);
+      if (size == 0)
+        return;
+    }
 
     // Allocate a chunk of memory.
     Header* header = reinterpret_cast<Header*>(memory_);
     memory_ += full_size;
     available_ -= full_size;
 
     // Datafill the header and name records. Memory must be zeroed. The |type|
     // is written last, atomically, to release all the other values.
     DCHECK_EQ(END_OF_VALUES, header->type.load(std::memory_order_relaxed));
     DCHECK_EQ(0, header->value_size.load(std::memory_order_relaxed));
@@ skipping 1031 matching lines @@
     : GlobalActivityTracker::ScopedThreadActivity(
           program_counter,
           nullptr,
           Activity::ACT_PROCESS_WAIT,
           ActivityData::ForProcess(process->Pid()),
           /*lock_allowed=*/true) {}
 #endif
 
 }  // namespace debug
 }  // namespace base