[PE] cc::DisplayItemList::TotalOpCount()

I found the reason that SPv175 has 10% less paint_op_count but about
1% more paint_op_memory_usage: we didn't count ops in sub-records.

Add cc::DisplayItemList::TotalOpCount() to count all ops.

Bug: 803867
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I0526ace84cc16775d5691e87b502544e64f5932e
Reviewed-on: https://chromium-review.googlesource.com/996316
Reviewed-by: Chris Harrelson <[email protected]>
Commit-Queue: Xianzhu Wang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#548653}
7 files changed