Fix chrome finder on linux/osx when process.env isn't populated (#2687)

.travis.yml

@@ -27,7 +27,7 @@ install:
 before_script:
   - gem install travis-artifacts
   - export DISPLAY=:99.0
-  - export LIGHTHOUSE_CHROMIUM_PATH="$(pwd)/chrome-linux/chrome"
+  - export CHROME_PATH="$(pwd)/chrome-linux/chrome"
   - sh -e /etc/init.d/xvfb start
   - sleep 3 # wait for xvfb to boot
   - yarn build-all

chrome-launcher/chrome-finder.ts

@@ -53,11 +53,17 @@ export function darwin() {
     {regex: /^\/Applications\/.*Chrome Canary.app/, weight: 101},
     {regex: /^\/Volumes\/.*Chrome.app/, weight: -2},
     {regex: /^\/Volumes\/.*Chrome Canary.app/, weight: -1},
-    {regex: new RegExp(process.env.LIGHTHOUSE_CHROMIUM_PATH), weight: 150},
-    {regex: new RegExp(process.env.CHROME_PATH), weight: 151}
   ];
-  // clang-format on
 
+  if (process.env.LIGHTHOUSE_CHROMIUM_PATH) {
+    priorities.push({regex: new RegExp(process.env.LIGHTHOUSE_CHROMIUM_PATH), weight: 150});
+  }
+
+  if (process.env.CHROME_PATH) {
+    priorities.push({regex: new RegExp(process.env.CHROME_PATH), weight: 151});
+  }
+
+  // clang-format on
   return sort(installations, priorities);
 }
 
@@ -124,12 +130,19 @@ export function linux() {
   }
 
   const priorities: Priorities = [
-    {regex: /chrome-wrapper$/, weight: 51}, {regex: /google-chrome-stable$/, weight: 50},
+    {regex: /chrome-wrapper$/, weight: 51},
+    {regex: /google-chrome-stable$/, weight: 50},
     {regex: /google-chrome$/, weight: 49},
-    {regex: new RegExp(process.env.LIGHTHOUSE_CHROMIUM_PATH), weight: 100},
-    {regex: new RegExp(process.env.CHROME_PATH), weight: 101}
   ];
 
+  if (process.env.LIGHTHOUSE_CHROMIUM_PATH) {
+    priorities.push({regex: new RegExp(process.env.LIGHTHOUSE_CHROMIUM_PATH), weight: 100});
+  }
+
+  if (process.env.CHROME_PATH) {
+    priorities.push({regex: new RegExp(process.env.CHROME_PATH), weight: 101});
+  }
+
   return sort(uniq(installations.filter(Boolean)), priorities);
 }