Set kMaxCategories to 300.

When running unittests, number of categories reach 253.
Max number needs to be increased.

Bug: 908002
Change-Id: Iaf8d449eb005b6a5b4e4a2524f913d3eeba54f41
Reviewed-on: https://chromium-review.googlesource.com/c/1373470
Reviewed-by: Primiano Tucci <primiano@chromium.org>
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615841}

base/trace_event/category_registry.h

@@ -93,7 +93,7 @@ class BASE_EXPORT CategoryRegistry {
   using CategoryInitializerFn = void (*)(TraceCategory*);
 
   // The max number of trace categories that can be recorded.
-  static constexpr size_t kMaxCategories = 250;
+  static constexpr size_t kMaxCategories = 300;
 
   // Checks that there is enough space for all builtin categories.
   static_assert(BuiltinCategories::Size() <= kMaxCategories,