chore(travis): temporary workaround for issue 1350

Temporarily use Dart SDK 1.6.0-dev.7.0 (instead of 1.6.0-dev.8.0)
to work around issue #1350 / dartbug 20500.

Closes #1353

Author: chirayuk

scripts/travis/setup.sh

@@ -7,8 +7,26 @@ echo Fetch Dart channel: $CHANNEL
 
 DART_SDK_ZIP=dartsdk-linux-x64-release.zip
 
-echo http://storage.googleapis.com/dart-archive/channels/$CHANNEL/release/latest/sdk/$DART_SDK_ZIP
-curl -L http://storage.googleapis.com/dart-archive/channels/$CHANNEL/release/latest/sdk/$DART_SDK_ZIP > $DART_SDK_ZIP
+# TODO(chirayu): Remove this once issue 1350 is fixed.
+SVN_REVISION=latest
+if [[ "$CHANNEL" == "dev" ]]; then
+  issue_1350_state=$(curl 'https://api.github.com/repos/angular/angular.dart/issues/1020' | python -c \
+                     'import sys, json; print(json.loads(sys.stdin.read())["state"])')
+  if [[ "$issue_1350_state" == "open" ]]; then
+    # Is there a newer dev SDK?
+    latest_version=$(curl 'https://storage.googleapis.com/dart-archive/channels/dev/release/latest/VERSION' | python -c \
+      'import sys, json; print(json.loads(sys.stdin.read())["version"])')
+    if [[ "$latest_version" == "1.6.0-dev.8.0" ]]; then
+      # Use prior working version (1.6.0-dev.7.0)
+      SVN_REVISION=38831
+    fi
+  fi
+fi
+
+URL=https://storage.googleapis.com/dart-archive/channels/$CHANNEL/release/$SVN_REVISION/sdk/$DART_SDK_ZIP
+echo $URL
+curl -L -O $URL
+
 echo Fetched new dart version $(unzip -p $DART_SDK_ZIP dart-sdk/version)
 rm -rf dart-sdk
 unzip $DART_SDK_ZIP > /dev/null