Revert "tools/luci-go: remove old way of mapping isolate"

This reverts commit 6bb055be.

Reason for revert: P0 bug https://crbug.com/865882

Original change's description:
> tools/luci-go: remove old way of mapping isolate
> 
> It's now only mapped via CIPD, which is the right solution going forward.
> 
> Bug: 851596,865541
> Change-Id: I25ddd0e059c818fafbc5587b06ff35b6c733a16e
> Reviewed-on: https://chromium-review.googlesource.com/1143448
> Commit-Queue: Marc-Antoine Ruel <maruel@chromium.org>
> Reviewed-by: John Budorick <jbudorick@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#576550}

TBR=maruel@chromium.org,tandrii@chromium.org,jbudorick@chromium.org

Change-Id: I2d432e9c80379c41e22b7a1cfdb4ea3f54586baa
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 851596, 865541
Reviewed-on: https://chromium-review.googlesource.com/1145020Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Commit-Queue: Sergiy Byelozyorov <sergiyb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576823}

DEPS

@@ -1704,6 +1704,44 @@ hooks = [
                 '-d', 'src/chrome/build',
     ],
   },
+  # Pull luci-go binaries (isolate, swarming) using checked-in hashes.
+  # TODO(maruel): Remove, https://crbug.com/851596
+  {
+    'name': 'luci-go_win',
+    'pattern': '.',
+    'condition': 'host_os == "win"',
+    'action': [ 'python',
+                'src/third_party/depot_tools/download_from_google_storage.py',
+                '--no_resume',
+                '--no_auth',
+                '--bucket', 'chromium-luci',
+                '-d', 'src/tools/luci-go/win64',
+    ],
+  },
+  {
+    'name': 'luci-go_mac',
+    'pattern': '.',
+    'condition': 'host_os == "mac"',
+    'action': [ 'python',
+                'src/third_party/depot_tools/download_from_google_storage.py',
+                '--no_resume',
+                '--no_auth',
+                '--bucket', 'chromium-luci',
+                '-d', 'src/tools/luci-go/mac64',
+    ],
+  },
+  {
+    'name': 'luci-go_linux',
+    'pattern': '.',
+    'condition': 'host_os == "linux"',
+    'action': [ 'python',
+                'src/third_party/depot_tools/download_from_google_storage.py',
+                '--no_resume',
+                '--no_auth',
+                '--bucket', 'chromium-luci',
+                '-d', 'src/tools/luci-go/linux64',
+    ],
+  },
   # Pull the Syzygy binaries, used for optimization and instrumentation.
   # Remove this as soon as the zap_timestamp.exe utility is no longer used.
   # See https://crbug.com/821764#c3.

tools/luci-go/.gitignore

 /isolate
 /isolate.exe
+/linux64/isolate
+/mac64/isolate
+/win64/isolate.exe
 .versions

tools/luci-go/linux64/isolate.sha1

+9734e966a14f9e26f86e38a020fcd7584248d285

tools/luci-go/mac64/isolate.sha1

+18561de57e944d096521838b4e6cb49e0cc1df23

tools/luci-go/win64/isolate.exe.sha1

+af227603890ea1d8c082b5caf15e46a6bf060a2e