Remove the weird range variants of String8::toLower() and String8::toUpper().

I want to remove these bad ASCII-only APIs completely, but it might be
easier to remove the range variants first.

Test: treehugger
Change-Id: I4c11f959a7bd8e670708cc03281ea72e9c461ff7
diff --git a/libutils/String8.cpp b/libutils/String8.cpp
index 3dc2026..fad130b 100644
--- a/libutils/String8.cpp
+++ b/libutils/String8.cpp
@@ -415,50 +415,28 @@
 
 void String8::toLower()
 {
-    toLower(0, size());
-}
+    const size_t length = size();
+    if (length == 0) return;
 
-void String8::toLower(size_t start, size_t length)
-{
-    const size_t len = size();
-    if (start >= len) {
-        return;
-    }
-    if (start+length > len) {
-        length = len-start;
-    }
-    char* buf = lockBuffer(len);
-    buf += start;
-    while (length > 0) {
+    char* buf = lockBuffer(length);
+    for (size_t i = length; i > 0; --i) {
         *buf = static_cast<char>(tolower(*buf));
         buf++;
-        length--;
     }
-    unlockBuffer(len);
+    unlockBuffer(length);
 }
 
 void String8::toUpper()
 {
-    toUpper(0, size());
-}
+    const size_t length = size();
+    if (length == 0) return;
 
-void String8::toUpper(size_t start, size_t length)
-{
-    const size_t len = size();
-    if (start >= len) {
-        return;
-    }
-    if (start+length > len) {
-        length = len-start;
-    }
-    char* buf = lockBuffer(len);
-    buf += start;
-    while (length > 0) {
+    char* buf = lockBuffer(length);
+    for (size_t i = length; i > 0; --i) {
         *buf = static_cast<char>(toupper(*buf));
         buf++;
-        length--;
     }
-    unlockBuffer(len);
+    unlockBuffer(length);
 }
 
 // ---------------------------------------------------------------------------