Add support for GCS deps

Also take out GCS calling logic from download_google_storage and
into call_google_storage.

GCS deps look like:
   'src/third_party/node/linux': {
       'dep_type': 'gcs',
       'condition': 'checkout_linux',
       'bucket': 'chromium-nodejs/20.11.0',
       'object_name': '46795170ff5df9831955f163f6966abde581c8af',
       'sha256sum': '887504c37404898ca41b896f448ee6d7fc24179d8fb6a4b79d028ab7e1b7153d',
   },

   'src/third_party/llvm-build/Release+Asserts': {
       'dep_type': 'gcs',
       'condition': 'checkout_linux',
       'bucket': 'chromium-browser-clang',
       'object_name': 'Linux_x64/clang-llvmorg-18-init-17730-gf670112a-2.tar.xz',
       'sha256sum': '1e46df9b4e63c074064d75646310cb76be2f19815997a8486987189d80f991e8',
   },

Example directory for src/third_party/node/linux after gclient sync:
- tar_file.gz is the downloaded file from GCS.
- node_linux_x64/ is extracted in its path.
- `hash` contains the sha of GCS filename.
```
chromium/src/ ->
   third_party/node/linux/ ->
       hash, tar_file.gz, node_linux_x64/
```

Bug: b/324418194
Change-Id: Ibcbbff27e211f194ddb8a08494af56570a84a12b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5299722
Commit-Queue: Stephanie Kim <kimstephanie@google.com>
Reviewed-by: Joanna Wang <jojwang@chromium.org>

testing_support/fake_repos.py

@@ -16,6 +16,7 @@ import random
 import re
 import socket
 import sys
+import tarfile
 import tempfile
 import textwrap
 import time
@@ -47,6 +48,9 @@ def read_tree(tree_root):
         for f in [join(root, f) for f in files if not f.startswith('.')]:
             filepath = f[len(tree_root) + 1:].replace(os.sep, '/')
             assert len(filepath) > 0, f
+            if tarfile.is_tarfile(join(root, f)):
+                tree[filepath] = 'tarfile'
+                continue
             with io.open(join(root, f), encoding='utf-8') as f:
                 tree[filepath] = f.read()
     return tree
@@ -210,7 +214,7 @@ class FakeReposBase(object):
 
 class FakeRepos(FakeReposBase):
     """Implements populateGit()."""
-    NB_GIT_REPOS = 21
+    NB_GIT_REPOS = 23
 
     def populateGit(self):
         # Testing:
@@ -881,6 +885,63 @@ deps = {
             },
         )
 
+        self._commit_git(
+            'repo_22', {
+                'DEPS':
+                textwrap.dedent("""\
+        vars = {}
+        deps = {
+          'src/gcs_dep': {
+            'bucket': '123bucket',
+            'object_name': 'deadbeef',
+            'dep_type': 'gcs',
+            'sha256sum': 'abcd123',
+          },
+          'src/another_gcs_dep': {
+            'bucket': '456bucket',
+            'object_name': 'Linux/llvmfile.tar.gz',
+            'dep_type': 'gcs',
+            'sha256sum': 'abcd123',
+          },
+        }"""),
+                'origin':
+                'git/repo_22@1\n'
+            })
+
+        self._commit_git(
+            'repo_23', {
+                'DEPS': """
+deps = {
+  'src/repo12': '/repo_12',
+}""",
+                'origin': 'git/repo_23@1\n',
+            })
+
+        self._commit_git(
+            'repo_23', {
+                'DEPS': """
+deps = {
+  'src/repo12': '/repo_12@refs/changes/1212',
+}""",
+                'origin': 'git/repo_23@2\n',
+            })
+
+        # src/repo12 is now a GCS dependency.
+        self._commit_git(
+            'repo_23', {
+                'DEPS': """
+deps = {
+  'src/repo12': {
+    'bucket': 'bucket123',
+    'object_name': 'path_to_file.tar.gz',
+    'dep_type': 'gcs',
+    'sha256sum': 'abcd123',
+  },
+}
+""",
+                'origin': 'git/repo_23@3\n'
+            })
+
 
 class FakeRepoSkiaDEPS(FakeReposBase):
     """Simulates the Skia DEPS transition in Chrome."""