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

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

Index: third_party/WebKit/Source/wtf/text/WTFString.cpp
diff --git a/third_party/WebKit/Source/wtf/text/WTFString.cpp b/third_party/WebKit/Source/wtf/text/WTFString.cpp
index b67387516f033f4813df7bf79234e99544ceb1a4..0c943b90ba91221d0c88732a910b47c1cf58a227 100644
--- a/third_party/WebKit/Source/wtf/text/WTFString.cpp
+++ b/third_party/WebKit/Source/wtf/text/WTFString.cpp
@@ -869,7 +869,7 @@ String String::make16BitFrom8BitSource(const LChar* source, size_t length)
     return result;
 }
 
-String String::fromUTF8(const LChar* stringStart, size_t length)
+String String::fromUTF8(const LChar* stringStart, size_t length, bool strict)
 {
     RELEASE_ASSERT(length <= std::numeric_limits<unsigned>::max());
 
@@ -887,7 +887,7 @@ String String::fromUTF8(const LChar* stringStart, size_t length)
 
     UChar* bufferCurrent = bufferStart;
     const char* stringCurrent = reinterpret_cast<const char*>(stringStart);
-    if (convertUTF8ToUTF16(&stringCurrent, reinterpret_cast<const char *>(stringStart + length), &bufferCurrent, bufferCurrent + buffer.size()) != conversionOK)
+    if (convertUTF8ToUTF16(&stringCurrent, reinterpret_cast<const char *>(stringStart + length), &bufferCurrent, bufferCurrent + buffer.size(), nullptr, strict) != conversionOK)
         return String();
 
     unsigned utf16Length = bufferCurrent - bufferStart;