Bug 4016329 do full string comparisons

Use full string comparisons instead of partial for
  file extension and MIME type.
Do case-insensitive comparison of MIME type and file extensions.
Fix error in comment for String8::getPathExtension.
Remove dead code -- StringTokenizer is unused.

Change-Id: I322be6235abbdaab5f7eafa48926dbb2cf46dc29
diff --git a/drm/common/DrmSupportInfo.cpp b/drm/common/DrmSupportInfo.cpp
index 3e02093..c0bff0e 100644
--- a/drm/common/DrmSupportInfo.cpp
+++ b/drm/common/DrmSupportInfo.cpp
@@ -45,7 +45,7 @@
     for (unsigned int i = 0; i < mMimeTypeVector.size(); i++) {
         const String8 item = mMimeTypeVector.itemAt(i);
 
-        if (String8("") != mimeType && item.find(mimeType) != -1) {
+        if (!strcasecmp(item.string(), mimeType.string())) {
             return true;
         }
     }
@@ -56,7 +56,7 @@
     for (unsigned int i = 0; i < mFileSuffixVector.size(); i++) {
         const String8 item = mFileSuffixVector.itemAt(i);
 
-        if (item.find(fileType) != -1) {
+        if (!strcasecmp(item.string(), fileType.string())) {
             return true;
         }
     }