Migrate from android::String isEmpty to empty

This empty method is different from the old one - it aligns with
std::string definition.

Bug: 295394788
Test: make checkbuild
Change-Id: I890b3dfa930002f4406e9d9aec024f94ada1cad0
diff --git a/drm/libmediadrm/DrmHalAidl.cpp b/drm/libmediadrm/DrmHalAidl.cpp
index 9e30708..7106d66 100644
--- a/drm/libmediadrm/DrmHalAidl.cpp
+++ b/drm/libmediadrm/DrmHalAidl.cpp
@@ -375,7 +375,7 @@
     sp<DrmHalAidl> drm = mDrm.promote();
     if (drm == NULL) {
         name.append("<deleted>");
-    } else if (drm->getPropertyStringInternal(String8("vendor"), name) != OK || name.isEmpty()) {
+    } else if (drm->getPropertyStringInternal(String8("vendor"), name) != OK || name.empty()) {
         name.append("<Get vendor failed or is empty>");
     }
     name.append("[");
@@ -947,12 +947,12 @@
 
     String8 vendor;
     String8 description;
-    if (getPropertyStringInternal(String8("vendor"), vendor) != OK || vendor.isEmpty()) {
+    if (getPropertyStringInternal(String8("vendor"), vendor) != OK || vendor.empty()) {
         ALOGE("Get vendor failed or is empty");
         vendor = "NONE";
     }
     if (getPropertyStringInternal(String8("description"), description) != OK ||
-        description.isEmpty()) {
+        description.empty()) {
         ALOGE("Get description failed or is empty.");
         description = "NONE";
     }