Convert CHECK to DCHECK in LayerTreeHost.

Since the other similar condition to this in LayerTreeHost is a DCHECK,
and since this one only seems to be hit on shutdown, let's make this a
DCHECK.

TBR=bokan@chromium.org

Bug: 845097, 845097
Change-Id: If4fd880076f9ddd0c16a8bf5e63a76bd2b2a69fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1598424Reviewed-by: James MacLean <wjmaclean@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: James MacLean <wjmaclean@chromium.org>
Cr-Commit-Position: refs/heads/master@{#657300}

cc/trees/layer_tree_host.cc

@@ -1282,10 +1282,10 @@ void LayerTreeHost::SetPageScaleFactorAndLimits(float page_scale_factor,
   DCHECK_GE(page_scale_factor, min_page_scale_factor);
   DCHECK_LE(page_scale_factor, max_page_scale_factor);
   // We should never process non-unit page_scale_delta for an OOPIF subframe.
-  // TODO(wjmaclean): Remove this check as a pre-condition to closing the bug.
+  // TODO(wjmaclean): Remove this dcheck as a pre-condition to closing the bug.
   // https://crbug.com/845097
-  CHECK(!settings_.is_layer_tree_for_subframe ||
-        page_scale_factor == page_scale_factor_)
+  DCHECK(!settings_.is_layer_tree_for_subframe ||
+         page_scale_factor == page_scale_factor_)
       << "Setting PSF in oopif subframe: old psf = " << page_scale_factor_
       << ", new psf = " << page_scale_factor;