PA: Suppress REALLOC_GROWTH_FACTOR_MITIGATION limit.

This patch is behind build flags. It has no impacts on Chrome.

The growth factor was previously applied starting from 12MB
allocations.

Instrumentation on Skia reveal this was too high and the nVidia
performance issue wasn't fixed. We need to suppress it, or at least to
make it lower.

Indeed, assuming we memory is reallocated repeated from 0 to 12MB,
using 4144 byte increment, we get currently get ~3036 iterations instead
of ~20:
- Prev: 12*1024*1024/4144                          = ~3036 iterations.
- Next: (log(12*1024*1024) - log(4144)) / log(1.5) =   ~20 iterations.

Bug: 351867706
Change-Id: If3f5365404f28e926b6e776a4260946949a15324
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6818351
Commit-Queue: Daniel Cheng <[email protected]>
Auto-Submit: Arthur Sonzogni <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1497709}
NOKEYCHECK=True
GitOrigin-RevId: 4bf11a8bcc9e9f2a04aca5cdfad1d55fd98790a9

Author: ArthurSonzogni

src/partition_alloc/partition_root.h

@@ -2424,7 +2424,7 @@ void* PartitionRoot::ReallocInline(void* ptr,
   // factor to the new size to avoid this issue. This workaround is only
   // intended to be used for Skia bots, and is not intended to be a general
   // solution.
-  if (new_size > old_usable_size && new_size > 12 << 20) {
+  if (new_size > old_usable_size) {
     // 1.5x growth factor.
     // Note that in case of integer overflow, the std::max ensures that the
     // new_size is at least as large as the old_usable_size.