[Android] Add support for installing older versions of installed apks.

build/android/devil/android/sdk/adb_wrapper.py

Index: build/android/devil/android/sdk/adb_wrapper.py
diff --git a/build/android/devil/android/sdk/adb_wrapper.py b/build/android/devil/android/sdk/adb_wrapper.py
index 3ab7ddc096a9dad266c15a48df30e2ced45ed4d4..5a1e4027e608f4746d235cc5d9e9074024d908f9 100644
--- a/build/android/devil/android/sdk/adb_wrapper.py
+++ b/build/android/devil/android/sdk/adb_wrapper.py
@@ -438,8 +438,9 @@ class AdbWrapper(object):
     return [a.strip() for a in
             self._RunDeviceAdbCmd(['jdwp'], timeout, retries).split('\n')]
 
-  def Install(self, apk_path, forward_lock=False, reinstall=False,
-              sd_card=False, timeout=60*2, retries=_DEFAULT_RETRIES):
+  def Install(self, apk_path, forward_lock=False, allow_downgrade=False,
+              reinstall=False, sd_card=False, timeout=60*2,
+              retries=_DEFAULT_RETRIES):
     """Install an apk on the device.
 
     Args:
@@ -449,6 +450,7 @@ class AdbWrapper(object):
       sd_card: (optional) If set installs on the SD card.
       timeout: (optional) Timeout per try in seconds.
       retries: (optional) Number of retries to attempt.
+      allow_downgrade: (optional) If set, allows for downgrades.

[jbudorick, 2015/12/08 16:44:56]

nit: same

[rnephew (Reviews Here), 2015/12/08 16:57:57]

Done.

     """
     VerifyLocalFileExists(apk_path)
     cmd = ['install']
@@ -458,6 +460,8 @@ class AdbWrapper(object):
       cmd.append('-r')
     if sd_card:
       cmd.append('-s')
+    if allow_downgrade:
+      cmd.append('-d')
     cmd.append(apk_path)
     output = self._RunDeviceAdbCmd(cmd, timeout, retries)
     if 'Success' not in output: