Fix use of Chrome Headless on Travis macOS builds

.travis.yml

@@ -9,6 +9,7 @@ addons:
   apt:
     packages:
     - libunwind8
+  chrome: stable
 mono: none
 os:
 - linux
@@ -29,6 +30,7 @@ install:
   - nvm use 8.9.4
   - npm install -g selenium-standalone
   - selenium-standalone install
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then export TEST_CHROME_BINARY=`which google-chrome-stable`; fi
   - export DOTNET_INSTALL_DIR="$PWD/.dotnetcli"
   - curl -sSL https://dot.net/v1/dotnet-install.sh | bash /dev/stdin --channel Current --version latest --install-dir "$DOTNET_INSTALL_DIR"
   - export PATH="$DOTNET_INSTALL_DIR:$PATH"

test/Microsoft.AspNetCore.Blazor.E2ETest/Infrastructure/BrowserFixture.cs

@@ -16,6 +16,16 @@ namespace Microsoft.AspNetCore.Blazor.E2ETest.Infrastructure
         {
             var opts = new ChromeOptions();
             opts.AddArgument("--headless");
+
+            // On Windows/Linux, we don't need to set opts.BinaryLocation
+            // But for Travis Mac builds we do
+            var binaryLocation = Environment.GetEnvironmentVariable("TEST_CHROME_BINARY");
+            if (!string.IsNullOrEmpty(binaryLocation))
+            {
+                opts.BinaryLocation = binaryLocation;
+                Console.WriteLine($"Set {nameof(ChromeOptions)}.{nameof(opts.BinaryLocation)} to {binaryLocation}");
+            }
+
             Browser = new RemoteWebDriver(opts);
         }