Method onMalloc

tests/fl/stl/allocator.cpp:1419–1422

                : mMallocCalls(mallocCalls), mMallocSizes(mallocSizes), mFreeCalls(freeCalls) {}
            
            void onMalloc(void* ptr, fl::size size) override {
                mMallocCalls.push_back(ptr);
                mMallocSizes.push_back(size);
            }
            
            void onFree(void* ptr) override {
                mFreeCalls.push_back(ptr);