sync compositor: pass simple gfx types by const ref

See bug for reasoning

BUG=159273

Review URL: https://codereview.chromium.org/1417893006

Cr-Commit-Position: refs/heads/master@{#356653}
void BrowserViewRenderer::OnAttachedToWindow(int width, int height) {
  TRACE_EVENT2("android_webview",
               "BrowserViewRenderer::OnAttachedToWindow",
               "width",
               width,
               "height",
               height);
  attached_to_window_ = true;
  size_.SetSize(width, height);
  UpdateCompositorIsActive();
}

void BrowserViewRenderer::OnAttachedToWindow(int width, int height) {
  TRACE_EVENT2("android_webview",
               "BrowserViewRenderer::OnAttachedToWindow",
               "width",
               width,
               "height",
               height);
  attached_to_window_ = true;
  size_.SetSize(width, height);
  UpdateCompositorIsActive();
}
