[Tracing] Adjust allocation register size for low-end devices

base/trace_event/heap_profiler_allocation_register.h

Index: base/trace_event/heap_profiler_allocation_register.h
diff --git a/base/trace_event/heap_profiler_allocation_register.h b/base/trace_event/heap_profiler_allocation_register.h
index 7c4ba99cd22c05eac3000d5d2c7ec42775b28d59..6642c39090683d89b56f7f5f9890912683e90715 100644
--- a/base/trace_event/heap_profiler_allocation_register.h
+++ b/base/trace_event/heap_profiler_allocation_register.h
@@ -60,6 +60,8 @@ class BASE_EXPORT AllocationRegister {
   };
 
   AllocationRegister();
+  AllocationRegister(uint32_t num_cells);

[Primiano Tucci (use gerrit), 2015/12/17 11:13:33]

+explicit. I guess you don't want integers to automatically cast into
AllocationRegisters :)

[seantopping, 2015/12/17 20:07:32]

Done.

+
   ~AllocationRegister();
 
   // Inserts allocation details into the table. If the address was present
@@ -112,7 +114,7 @@ class BASE_EXPORT AllocationRegister {
   // not an option). A value of ~3M entries is large enough to handle spikes in
   // the number of allocations, and modest enough to require no more than a few
   // dozens of MiB of address space.
-  static const uint32_t kNumCells = kNumBuckets * 10;
+  static const uint32_t kNumCellsPerBucket = 10;
 
   // Returns a value in the range [0, kNumBuckets - 1] (inclusive).
   static uint32_t Hash(void* address);
@@ -136,6 +138,9 @@ class BASE_EXPORT AllocationRegister {
   // from the free list or by taking a fresh cell) and returns its index.
   CellIndex GetFreeCell();
 
+  // The maximum number of cells which can be allocated.
+  uint32_t const num_cells_;
+
   // The array of cells. This array is backed by mmapped memory. Lower indices
   // are accessed first, higher indices are only accessed when required. In
   // this way, even if a huge amount of address space has been mmapped, only