Have (new URLSearchParams(initString)) skip initial '?'.

third_party/WebKit/Source/core/dom/URLSearchParams.cpp

Index: third_party/WebKit/Source/core/dom/URLSearchParams.cpp
diff --git a/third_party/WebKit/Source/core/dom/URLSearchParams.cpp b/third_party/WebKit/Source/core/dom/URLSearchParams.cpp
index 5fbe139215e0bffd8ac5ce2a428b58325a4f0509..5e3493b5ef114cedc23267b86fd886a103b47a22 100644
--- a/third_party/WebKit/Source/core/dom/URLSearchParams.cpp
+++ b/third_party/WebKit/Source/core/dom/URLSearchParams.cpp
@@ -38,8 +38,12 @@ private:
 
 URLSearchParams* URLSearchParams::create(const URLSearchParamsInit& init)
 {
-    if (init.isUSVString())
-        return new URLSearchParams(init.getAsUSVString());
+    if (init.isUSVString()) {
+        const String& queryString = init.getAsUSVString();
+        if (queryString.startsWith('?'))
+            return new URLSearchParams(queryString.substring(1));
+        return new URLSearchParams(queryString);
+    }
     if (init.isURLSearchParams())
         return new URLSearchParams(init.getAsURLSearchParams());