This surfaces the memory page count for the maximum policy size as a constant,
so that we can rely on it in our code. It also reverts it to 14, the value
it was set to before the latest chromium sandbox update.

diff --git a/security/sandbox/chromium/sandbox/win/src/sandbox_policy.h b/security/sandbox/chromium/sandbox/win/src/sandbox_policy.h
index 4d9d8f270890..bffab2fae890 100644
--- a/security/sandbox/chromium/sandbox/win/src/sandbox_policy.h
+++ b/security/sandbox/chromium/sandbox/win/src/sandbox_policy.h
@@ -10,16 +10,19 @@
 
 #include "base/containers/span.h"
 #include "base/memory/scoped_refptr.h"
 #include "sandbox/win/src/sandbox_types.h"
 #include "sandbox/win/src/security_level.h"
 
 namespace sandbox {
 
+// Number of memory pages to allow for the policy storage.
+constexpr size_t kPolMemPageCount = 14;
+
 class AppContainer;
 
 // Desktop used to launch child, controls GetDesktop().
 enum class Desktop {
   // Child is launched without changing the desktop.
   kDefault,
   // Child is launched using the alternate desktop.
   kAlternateDesktop,
diff --git a/security/sandbox/chromium/sandbox/win/src/sandbox_policy_base.cc b/security/sandbox/chromium/sandbox/win/src/sandbox_policy_base.cc
index 2559133d772b..3395e9cadc07 100644
--- a/security/sandbox/chromium/sandbox/win/src/sandbox_policy_base.cc
+++ b/security/sandbox/chromium/sandbox/win/src/sandbox_policy_base.cc
@@ -44,17 +44,17 @@
 
 namespace sandbox {
 namespace {
 
 // The standard windows size for one memory page.
 constexpr size_t kOneMemPage = 4096;
 // The IPC and Policy shared memory sizes.
 constexpr size_t kIPCMemSize = kOneMemPage * 2;
-constexpr size_t kPolMemSize = kOneMemPage * 6;
+constexpr size_t kPolMemSize = kOneMemPage * kPolMemPageCount;
 
 // Offset of pShimData in ntdll!_PEB.
 #if defined(_WIN64)
 // This is the same on x64 and arm64.
 constexpr ptrdiff_t kShimDataOffset = 0x2d8;
 #else
 constexpr ptrdiff_t kShimDataOffset = 0x1e8;
 #endif