Prevent duplicate content script injection defined in manifest.json

chrome/test/data/extensions/api_test/content_scripts/duplicate_script_injection/manifest.json

Index: chrome/test/data/extensions/api_test/content_scripts/duplicate_script_injection/manifest.json
diff --git a/chrome/test/data/extensions/api_test/content_scripts/duplicate_script_injection/manifest.json b/chrome/test/data/extensions/api_test/content_scripts/duplicate_script_injection/manifest.json
new file mode 100644
index 0000000000000000000000000000000000000000..980e1dd9f9c9af3005f469d30d83530f725c7215
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/content_scripts/duplicate_script_injection/manifest.json
@@ -0,0 +1,20 @@
+{
+  "name": "duplicate script injection",
+  "version": "0.0.1",
+  "manifest_version": 2,
+  "description": "Tests that content scripts assigned to two overlapping url matches are not injected twice. Note this can be extended to N matches",
+  "background": {

[Devlin, 2016/07/15 22:43:26]

nitty nit:
"background": {},

(i.e., open and close brace on one line)

[catmullings, 2016/07/19 15:53:30]

Done.

+  },
+  "content_scripts": [
+    {
+      "matches": ["*://*.google.com/*"],
+      "js": ["test.js"],
+      "run_at": "document_end"
+    },
+    {
+      "matches": ["*://maps.google.com/*"],
+      "js": ["test.js"],
+      "run_at": "document_end"
+    }

[Devlin, 2016/07/15 22:43:27]

I wonder if we should make this a little more intense by having another script
that is deliberately injected twice because it's injected at different times in
the load process. e.g. adding a rule
{
  "matches": ["*://maps.google.com/*"],
  "js": ["should_run_twice.js"],
  "run_at": "document_start"
}
and then add the "should_run_twice.js" entry to either of the rules above.

WDYT?

[catmullings, 2016/07/19 15:53:30]

Done.

+  ]
+}