Reland of Update references to linux_precise_blink_rel in src. (patchset #1 id:1 of https://codereview.chromium.org/2504373002/ )

Reason for revert:
linux_trusty_blink_rel is now working, with more capacity

Original issue's description:
> Revert of Update references to linux_precise_blink_rel in src. (patchset #1 id:1 of https://codereview.chromium.org/2470243002/ )
>
> Reason for revert:
> Submitting this before more capacity was added to linux_trusty_blink_rel caused that builder to get too busy (http://crbug.com/665246); should be able to reland after http://crbug.com/665917 is fixed.
>
> Original issue's description:
> > Update references to linux_precise_blink_rel in src.
> >
> > Reason: We're planning to drop support for Linux Precise for layout tests.
> >
> > BUG=660580
> > CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
> >
> > Committed: https://crrev.com/ab87a374dd800813751d405a6fdf3a4c4b3066f7
> > Cr-Commit-Position: refs/heads/master@{#430673}
>
> TBR=dpranke@chromium.org,enne@chromium.org
> # Not skipping CQ checks because original CL landed more than 1 days ago.
> BUG=660580
>
> Committed: https://crrev.com/745af0be287c0ef9e2af4694e80760931574945c
> Cr-Commit-Position: refs/heads/master@{#432545}

TBR=dpranke@chromium.org,enne@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=660580

Review-Url: https://codereview.chromium.org/2509333002
Cr-Commit-Position: refs/heads/master@{#432914}

cc/PRESUBMIT.py

@@ -339,7 +339,7 @@ def PostUploadHook(cl, change, output_api):
     return []
 
   bots = [
-    'master.tryserver.blink:linux_precise_blink_rel',
+    'master.tryserver.blink:linux_trusty_blink_rel',
   ]
 
   results = []

docs/updating_clang.md

@@ -13,7 +13,7 @@
     git cl try -m tryserver.chromium.mac -b mac_chromium_asan_rel_ng &&
     git cl try -m tryserver.chromium.linux -b linux_chromium_chromeos_dbg_ng \
       -b linux_chromium_chromeos_asan_rel_ng -b linux_chromium_msan_rel_ng &&
-    git cl try -m tryserver.blink -b linux_precise_blink_rel
+    git cl try -m tryserver.blink -b linux_trusty_blink_rel
 ```
 1.  Commit roll CL from the first step
 1.  The bots will now pull the prebuilt binary, and goma will have a matching