Remove DEFINE_CONTENT_DATA_TYPE_CASTS use from content_data.h

The primary motivation of this CL is to replace
ToCounterContentData with To<CounterContentData>,
ToQuoteContentData with To<QuoteContentData>,
ToImageContentData with To<ImageContentData>,
ToTextContentData with To<TextContentData>.

This CL also ports other dependent files to refer to a new template
function name.

Bug: 891908
Change-Id: I0ace9d668a090a2d4ef9f90b57aa73b65227f15f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1533677
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Abhijeet Kandalkar <abhijeet@igalia.com>
Cr-Commit-Position: refs/heads/master@{#642904}
6 files changed