Use test fonts in the test shell and remove custom font installation on Travis. (flutter#7250)

Author: chinmaygarde

.travis.yml

@@ -6,7 +6,6 @@ addons:
       - ubuntu-toolchain-r-test # if we don't specify this, the libstdc++6 we get is the wrong version
     packages:
       - libstdc++6
-      - fonts-droid
 install:
   - gem install coveralls-lcov
   - npm install -g firebase-tools@">=3.0.4 <3.1.0"

bin/internal/engine.version

@@ -1 +1 @@
-2f32e8054ddac59150e170fdaf8a601ca00f5989
+b65e1b91b5a46d710fd9c71c0a9a69f2a035265f

packages/flutter_tools/lib/src/test/flutter_platform.dart

@@ -67,6 +67,7 @@ Future<Process> _startProcess(String mainPath, { String packages, int observator
   arguments.addAll(<String>[
     '--enable-dart-profiling',
     '--non-interactive',
+    '--use-test-fonts',
     '--enable-checked-mode',
     '--packages=$packages',
     mainPath