Introduce String::fromUTF8Lenient() and use it for cache_name in CacheStorage API.

third_party/WebKit/Source/wtf/text/WTFString.h

Index: third_party/WebKit/Source/wtf/text/WTFString.h
diff --git a/third_party/WebKit/Source/wtf/text/WTFString.h b/third_party/WebKit/Source/wtf/text/WTFString.h
index 0b1b4ea8fd153ea6f4baae0726940c95b34a97f1..b05dbc89a2a191a181dc02421220670d2ce28148 100644
--- a/third_party/WebKit/Source/wtf/text/WTFString.h
+++ b/third_party/WebKit/Source/wtf/text/WTFString.h
@@ -428,9 +428,10 @@ public:
 
     static String make16BitFrom8BitSource(const LChar*, size_t);
 
-    // String::fromUTF8 will return a null string if
-    // the input data contains invalid UTF-8 sequences.
-    static String fromUTF8(const LChar*, size_t);
+    // String::fromUTF8 will return a null string if the input data contains
+    // invalid UTF-8 sequences. When |strict| is false, isolated surrogates are
+    // converted.
+    static String fromUTF8(const LChar*, size_t, bool strict = true);
     static String fromUTF8(const LChar*);
     static String fromUTF8(const char* s, size_t length) { return fromUTF8(reinterpret_cast<const LChar*>(s), length); }
     static String fromUTF8(const char* s) { return fromUTF8(reinterpret_cast<const LChar*>(s)); }
@@ -441,6 +442,10 @@ public:
     static String fromUTF8WithLatin1Fallback(const LChar*, size_t);
     static String fromUTF8WithLatin1Fallback(const char* s, size_t length) { return fromUTF8WithLatin1Fallback(reinterpret_cast<const LChar*>(s), length); }
 
+    // Helper methods to call fromUTF8() with |strict| = false.
+    static String fromUTF8Lenient(const LChar* s, size_t length) { return fromUTF8(s, length, false); }
+    static String fromUTF8Lenient(const char* s, size_t length) { return fromUTF8Lenient(reinterpret_cast<const LChar*>(s), length); }
+
     bool containsOnlyASCII() const;
     bool containsOnlyLatin1() const;
     bool containsOnlyWhitespace() const { return !m_impl || m_impl->containsOnlyWhitespace(); }