Gdb macro jfv on an object will print it as a feedback vector.
Printouts look like this:

DebugPrint: 0x5dc0d2ad: [TypeFeedbackVector]
 - length: 12
 - ics with type info: 3
 - generic ics: 0
 ICSlot 0 CALL_IC MONOMORPHIC
  [4]: 0x5dc0d365 WeakCell for 0x5dc0cd69 <JS Function foo (SharedFunctionInfo 0x5dc0cb0d)>
  [5]: 0x4203c4c1 <Code: HANDLER>
 ICSlot 1 LOAD_IC MONOMORPHIC
  [6]: 0x5dc0d1f5 WeakCell for 0x3a710481 <Map(FAST_HOLEY_SMI_ELEMENTS)>
  [7]: 0x4203a1c1 <Code: HANDLER>
 ICSlot 2 LOAD_IC UNINITIALIZED
  [8]: 0x3060d045 <Symbol: 711234650 <String[20]: uninitialized_symbol>>
  [9]: 0x3060d045 <Symbol: 711234650 <String[20]: uninitialized_symbol>>
 ICSlot 3 LOAD_IC MONOMORPHIC
  [10]: 0x5dc0d3b5 WeakCell for 0x3a710d71 <Map(FAST_HOLEY_ELEMENTS)>
  [11]: 0x4202af01 <Code: HANDLER>

BUG=

Review URL: https://codereview.chromium.org/1225403005

Cr-Commit-Position: refs/heads/master@{#29679}