Set device to Nexus 4 and re-enable API 16, 17, and 18 emulator tests.

Fixes #2738.

Author: sjudd

.travis.yml

@@ -20,10 +20,9 @@ env:
   matrix:
     - COMPONENT=unit
     - COMPONENT=firebase
-      # TODO(#2738): Re-enable these when we find a fix.
-      #    - COMPONENT=instrumentation ANDROID_TARGET=16
-      #    - COMPONENT=instrumentation ANDROID_TARGET=17
-      #    - COMPONENT=instrumentation ANDROID_TARGET=18
+    - COMPONENT=instrumentation ANDROID_TARGET=16
+    - COMPONENT=instrumentation ANDROID_TARGET=17
+    - COMPONENT=instrumentation ANDROID_TARGET=18
     - COMPONENT=instrumentation ANDROID_TARGET=19
     - COMPONENT=instrumentation ANDROID_TARGET=21
     - COMPONENT=instrumentation ANDROID_TARGET=22

scripts/travis_create_emulator.sh

@@ -5,7 +5,7 @@ set -e
 target="system-images;android-${ANDROID_TARGET};default;armeabi-v7a"
 echo y | sdkmanager --update
 echo y | sdkmanager --install $target
-avdmanager create avd --force -n test -k $target --device "Nexus 5X" -c 2000M
+avdmanager create avd --force -n test -k $target --device "Nexus 4" -c 2048M
 QEMU_AUDIO_DRV=none $ANDROID_HOME/emulator/emulator -avd test -no-window -memory 2048 &
 
 exit 0