add replace_char() method to SkString API (skbug.com/2651)

src/core/SkString.cpp

Index: src/core/SkString.cpp
diff --git a/src/core/SkString.cpp b/src/core/SkString.cpp
index ba1da4136893dffcbc5e1ac8252d9e3a4118a977..f793c44dce8b8d4001ae0d7e16585ee00c9dedf1 100644
--- a/src/core/SkString.cpp
+++ b/src/core/SkString.cpp
@@ -555,6 +555,19 @@ void SkString::insertScalar(size_t offset, SkScalar value) {
     this->insert(offset, buffer, stop - buffer);
 }
 
+void SkString::replaceChar(char oldChar, char newChar) {
+    if (this->isEmpty() || oldChar == newChar) {
+        return;
+    }
+    size_t len = this->size();
+    char* writable = this->writable_str();
+    for (size_t i = 0 ; i < len ; ++i) {
+        if (oldChar == writable[i]) {
+            writable[i] = newChar;
+        }
+    }
+}
+
 void SkString::printf(const char format[], ...) {
     char    buffer[kBufferSize];
     ARGS_TO_BUFFER(format, buffer, kBufferSize);