Chrome Version: 59.0.3071.109
OS: Linux

What steps will reproduce the problem?
(1) file.h API accepts `char*` and  `const char*` for data. Instead it should accept `void*` and `const void*`

What is the expected result?
By accepting `void*`, it is easier to use since:
  - semantics are more clear: it accepts an opaque buffer
  - users don't need to `reinterpret_cast<>` in order to use it 
  - real example: if you have an `std::vector<uint8_t>` you have to `reinterprect_cast<>()` before calling `WriteAtCurrentPos()`


What happens instead?
  - it only accepts `char*` as destination buffer, and `const char*` as source buffer.