Support multiple installation of avd configs

This is done by specifying a common CIPD root
<chromium_src>/.android_emulator, and installing each avd config under
a separate sub directory.

Bug: 1278016
Change-Id: Iaaed9542a74c1257478fd9e220e9f13df97c1c2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3482176
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Haiyang Pan <hypan@google.com>
Cr-Commit-Position: refs/heads/main@{#974269}

.gitignore

@@ -61,6 +61,8 @@ Thumbs.db
 rust-project.json
 v8.log
 vs-chromium-project.txt
+# Store android emulator artifacts, used by //tools/android/avd/avd.py
+/.android_emulator/
 /.clangd
 /.clangd/
 /.clangd-index/

build/android/pylib/local/emulator/avd.py

@@ -26,6 +26,10 @@
 from pylib.local.emulator import ini
 from pylib.local.emulator.proto import avd_pb2
 
+# A common root directory to store the CIPD packages for creating or starting
+# the emulator instance, e.g. emulator binary, system images, AVDs.
+COMMON_CIPD_ROOT = os.path.join(constants.DIR_SOURCE_ROOT, '.android_emulator')
+
 _ALL_PACKAGES = object()
 _DEFAULT_AVDMANAGER_PATH = os.path.join(
     constants.ANDROID_SDK_ROOT, 'cmdline-tools', 'latest', 'bin', 'avdmanager')
@@ -193,10 +197,10 @@ def __init__(self, avd_proto_path):
     self.avd_proto_path = avd_proto_path
     self._config = _Load(avd_proto_path)
 
-    self._emulator_home = os.path.join(constants.DIR_SOURCE_ROOT,
+    self._emulator_home = os.path.join(COMMON_CIPD_ROOT,
                                        self._config.avd_package.dest_path)
     self._emulator_sdk_root = os.path.join(
-        constants.DIR_SOURCE_ROOT, self._config.emulator_package.dest_path)
+        COMMON_CIPD_ROOT, self._config.emulator_package.dest_path)
     self._emulator_path = os.path.join(self._emulator_sdk_root, 'emulator',
                                        'emulator')
 
@@ -491,7 +495,7 @@ def _IterVersionedCipdPackages(self, packages):
         pkgs_by_dir[pkg.dest_path].append(pkg)
 
     for pkg_dir, pkgs in pkgs_by_dir.items():
-      cipd_root = os.path.join(constants.DIR_SOURCE_ROOT, pkg_dir)
+      cipd_root = os.path.join(COMMON_CIPD_ROOT, pkg_dir)
       yield cipd_root, pkgs
 
   def _InstallCipdPackages(self, packages):

build/android/pylib/local/emulator/proto/avd.proto

@@ -14,7 +14,7 @@ message CIPDPackage {
   // Ignored when creating AVD packages.
   string version = 2;
   // Path into which the package should be installed.
-  // src-relative.
+  // relative to pylib.local.emulator.avd.COMMON_CIPD_ROOT.
   string dest_path = 3;
 }