Reverts third_party/protobuf: Update to HEAD (f52e188fe4)

third_party/protobuf/java/core/src/main/java/com/google/protobuf/Descriptors.java

Index: third_party/protobuf/java/core/src/main/java/com/google/protobuf/Descriptors.java
diff --git a/third_party/protobuf/java/core/src/main/java/com/google/protobuf/Descriptors.java b/third_party/protobuf/java/core/src/main/java/com/google/protobuf/Descriptors.java
index 38346f1559fb2192c7b32b278d49f73dd8fe0132..e00ea342ea0c3f2c59fbd80126b4e71d149b4c0d 100644
--- a/third_party/protobuf/java/core/src/main/java/com/google/protobuf/Descriptors.java
+++ b/third_party/protobuf/java/core/src/main/java/com/google/protobuf/Descriptors.java
@@ -871,10 +871,6 @@ public final class Descriptors {
         nestedTypes[i].setProto(proto.getNestedType(i));
       }
 
-      for (int i = 0; i < oneofs.length; i++) {
-        oneofs[i].setProto(proto.getOneofDecl(i));
-      }
-
       for (int i = 0; i < enumTypes.length; i++) {
         enumTypes[i].setProto(proto.getEnumType(i));
       }
@@ -1212,20 +1208,33 @@ public final class Descriptors {
       private final Object defaultDefault;
     }
 
-    // This method should match exactly with the ToJsonName() function in C++
-    // descriptor.cc.
-    private static String fieldNameToJsonName(String name) {
+    // TODO(xiaofeng): Implement it consistently across different languages. See b/24751348.
+    private static String fieldNameToLowerCamelCase(String name) {
       StringBuilder result = new StringBuilder(name.length());
       boolean isNextUpperCase = false;
       for (int i = 0; i < name.length(); i++) {
         Character ch = name.charAt(i);
-        if (ch == '_') {
-          isNextUpperCase = true;
-        } else if (isNextUpperCase) {
-          result.append(Character.toUpperCase(ch));
+        if (Character.isLowerCase(ch)) {
+          if (isNextUpperCase) {
+            result.append(Character.toUpperCase(ch));
+          } else {
+            result.append(ch);
+          }
           isNextUpperCase = false;
-        } else {
+        } else if (Character.isUpperCase(ch)) {
+          if (i == 0) {
+            // Force first letter to lower-case.
+            result.append(Character.toLowerCase(ch));
+          } else {
+            // Capital letters after the first are left as-is.
+            result.append(ch);
+          }
+          isNextUpperCase = false;
+        } else if (Character.isDigit(ch)) {
           result.append(ch);
+          isNextUpperCase = false;
+        } else {
+          isNextUpperCase = true;
         }
       }
       return result.toString();
@@ -1244,7 +1253,7 @@ public final class Descriptors {
       if (proto.hasJsonName()) {
         jsonName = proto.getJsonName();
       } else {
-        jsonName = fieldNameToJsonName(proto.getName());
+        jsonName = fieldNameToLowerCamelCase(proto.getName());
       }
 
       if (proto.hasType()) {
@@ -2123,7 +2132,7 @@ public final class Descriptors {
           // Can't happen, because addPackage() only fails when the name
           // conflicts with a non-package, but we have not yet added any
           // non-packages at this point.
-          throw new AssertionError(e);
+          assert false;
         }
       }
     }
@@ -2504,10 +2513,6 @@ public final class Descriptors {
 
     public int getFieldCount() { return fieldCount; }
 
-    public OneofOptions getOptions() {
-      return proto.getOptions();
-    }
-
     /** Get a list of this message type's fields. */
     public List<FieldDescriptor> getFields() {
       return Collections.unmodifiableList(Arrays.asList(fields));
@@ -2517,10 +2522,6 @@ public final class Descriptors {
       return fields[index];
     }
 
-    private void setProto(final OneofDescriptorProto proto) {
-      this.proto = proto;
-    }
-
     private OneofDescriptor(final OneofDescriptorProto proto,
                             final FileDescriptor file,
                             final Descriptor parent,