add post-mortem metadata for frames type

Previously (and still currently for some of them), post-mortem debugging
tools were using StandardFrameConstants::kContextOffset as the offset to
get the value that represents a frame's type.

However since https://codereview.chromium.org/1696043002, a new, more
general offset was introduced:
CommonFrameConstants::kContextOrFrameTypeOffset.

In order for post-mortem debugging tools to use this constant, it is
included in the generated post-mortem metadata.

R=danno@chromium.org,bmeurer@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2655553006
Cr-Commit-Position: refs/heads/master@{#42746}

tools/gen-postmortem-metadata.py

@@ -155,6 +155,8 @@ consts_misc = [
     { 'name': 'bit_field3_number_of_own_descriptors_shift',
         'value': 'Map::NumberOfOwnDescriptorsBits::kShift' },
 
+    { 'name': 'off_fp_context_or_frame_type',
+        'value': 'CommonFrameConstants::kContextOrFrameTypeOffset'},
     { 'name': 'off_fp_context',
         'value': 'StandardFrameConstants::kContextOffset' },
     { 'name': 'off_fp_constant_pool',