printing: Remove CHECKs used to investigate crash

CHECKs were added to investigate the cause of the crashes occurring in
the PrintRenderFrameHelper when OnPrintPreviewDialogClosed() is called.
Remove these CHECKs now that they are no longer needed for the
investigation.

Bug: 1019847
Change-Id: I38b8c2ff4d7b467871a076d0f19a96665f163858
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2149284Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Jesse Schettler <jschettler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758978}

components/printing/renderer/print_render_frame_helper.cc

@@ -1289,10 +1289,6 @@ void PrintRenderFrameHelper::PrintPreview(base::Value settings) {
 
 void PrintRenderFrameHelper::OnPrintPreviewDialogClosed() {
   ScopedIPC scoped_ipc(weak_ptr_factory_.GetWeakPtr());
-  // TODO(jschettler): Remove these CHECKs when finished investigating
-  // https://crbug.com/1019847.
-  CHECK(!render_frame_gone_);
-  CHECK(print_preview_context_.source_frame());
   print_preview_context_.source_frame()->DispatchAfterPrintEvent();
 }
 #endif  // BUILDFLAG(ENABLE_PRINT_PREVIEW)
@@ -2637,9 +2633,7 @@ void PrintRenderFrameHelper::PrintPreviewContext::set_error(
 
 blink::WebLocalFrame*
 PrintRenderFrameHelper::PrintPreviewContext::source_frame() {
-  // TODO(jschettler): Change this back to DCHECK when finished investigating
-  // https://crbug.com/1019847.
-  CHECK(state_ != UNINITIALIZED);
+  DCHECK(state_ != UNINITIALIZED);
   return source_frame_.GetFrame();
 }