Validate all incoming WebGLObjects.

A few entry points were missing the correct validation.

Tested with improved conformance tests in
https://github.com/KhronosGroup/WebGL/pull/2654 .

Bug: 848914
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Ib98a61cc5bf378d1b3338b04acd7e1bc4c2fe008
Reviewed-on: https://chromium-review.googlesource.com/1086718
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565016}
void WebGL2RenderingContextBase::clearBufferiv(GLenum buffer,
                                               GLint drawbuffer,
                                               MaybeShared<DOMInt32Array> value,
                                               GLuint src_offset) {
  if (isContextLost() ||
      !ValidateClearBuffer("clearBufferiv", buffer, value.View()->length(),
                           src_offset))
    return;

  ScopedRGBEmulationColorMask emulation_color_mask(this, color_mask_,
                                                   drawing_buffer_.get());

  ContextGL()->ClearBufferiv(buffer, drawbuffer,
                             value.View()->DataMaybeShared() + src_offset);
  UpdateBuffersToAutoClear(kClearBufferiv, buffer, drawbuffer);
}

void WebGL2RenderingContextBase::clearBufferiv(GLenum buffer,
                                               GLint drawbuffer,
                                               MaybeShared<DOMInt32Array> value,
                                               GLuint src_offset) {
  if (isContextLost() ||
      !ValidateClearBuffer("clearBufferiv", buffer, value.View()->length(),
                           src_offset))
    return;

  ScopedRGBEmulationColorMask emulation_color_mask(this, color_mask_,
                                                   drawing_buffer_.get());

  ContextGL()->ClearBufferiv(buffer, drawbuffer,
                             value.View()->DataMaybeShared() + src_offset);
  UpdateBuffersToAutoClear(kClearBufferiv, buffer, drawbuffer);
}
