cc: Add const versions of operator* to layer iterators.

cc: Add const versions of operator* to layer iterators.

This patch adds const versions of operator* for layer iterators, so
that we can use them for sorting/heapifying the iterators.

R=reveman

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=285038

[vmpstr, 2014-07-22 19:46:36]

PTAL

[reveman, 2014-07-22 19:48:40]

lgtm

[vmpstr, 2014-07-22 19:51:09]

The CQ bit was checked by vmpstr@chromium.org

[commit-bot: I haz the power, 2014-07-22 19:53:24]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/vmpstr@chromium.org/413603002/1

[commit-bot: I haz the power, 2014-07-22 23:11:26]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_aosp on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_aosp/builds/9...)
  android_chromium_gn_compile_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_chromium_gn_c...)
  android_clang_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_clang_dbg/bui...)
  android_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg/builds/20...)
  linux_chromium_chromeos_clang_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_chrome...)
  linux_chromium_chromeos_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_chrome...)
  linux_chromium_clang_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_clang_...)
  linux_chromium_gn_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_gn_rel...)
  linux_chromium_rel_swarming on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_rel_sw...)
  mac_chromium_compile_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/mac_chromium_compile_...)
  mac_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/mac_chromium_rel/buil...)
  win8_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win8_chromium_rel/bui...)
  win_chromium_compile_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_compile_...)
  win_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_rel/buil...)
  win_chromium_x64_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_x64_rel/...)
  linux_gpu on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/linux_gpu/builds/...)
  mac_gpu on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/mac_gpu/builds/31745)
  win_gpu on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu/builds/36294)

[commit-bot: I haz the power, 2014-07-22 23:19:36]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-07-22 23:19:37]

Try jobs failed on following builders:
  android_clang_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_clang_dbg/bui...)
  android_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg/builds/20...)
  mac_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/mac_chromium_rel/buil...)

[vmpstr, 2014-07-23 02:09:42]

The CQ bit was checked by vmpstr@chromium.org

[commit-bot: I haz the power, 2014-07-23 02:10:32]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/vmpstr@chromium.org/413603002/1

[commit-bot: I haz the power, 2014-07-23 04:11:28]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  mac_chromium_compile_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/mac_chromium_compile_...)

[commit-bot: I haz the power, 2014-07-23 06:08:55]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-07-23 06:08:56]

Try jobs failed on following builders:
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[vmpstr, 2014-07-23 06:25:26]

The CQ bit was checked by vmpstr@chromium.org

[commit-bot: I haz the power, 2014-07-23 06:29:38]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/vmpstr@chromium.org/413603002/1

[commit-bot: I haz the power, 2014-07-23 07:25:41]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[commit-bot: I haz the power, 2014-07-23 08:13:03]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-07-23 08:13:04]

Try jobs failed on following builders:
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[vmpstr, 2014-07-23 15:53:07]

The CQ bit was checked by vmpstr@chromium.org

[commit-bot: I haz the power, 2014-07-23 15:54:25]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/vmpstr@chromium.org/413603002/1

[commit-bot: I haz the power, 2014-07-23 16:34:23]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[commit-bot: I haz the power, 2014-07-23 17:14:15]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-07-23 17:14:16]

Try jobs failed on following builders:
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[vmpstr, 2014-07-23 17:39:42]

The CQ bit was checked by vmpstr@chromium.org

[commit-bot: I haz the power, 2014-07-23 17:40:12]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/vmpstr@chromium.org/413603002/1

[commit-bot: I haz the power, 2014-07-23 18:49:12]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[commit-bot: I haz the power, 2014-07-23 20:57:19]

Change committed as 285038