Log Message:
protobuf: updated to 3.9.0

Protocol Buffers v3.9.0

C++

Optimize and simplify implementation of RepeatedPtrFieldBase
Don't create unnecessary unknown field sets.
Remove branch from accessors to repeated field element array.
Added delimited parse and serialize util.
Reduce size by not emitting constants for fieldnumbers
Fix a bug when comparing finite and infinite field values with explicit tolerances.
TextFormat::Parser should use a custom Finder to look up extensions by number if \ 
one is provided.
Add MessageLite::Utf8DebugString() to make MessageLite more compatible with Message.
Fail fast for better performance in DescriptorPool::FindExtensionByNumber() if \ 
descriptor has no defined extensions.
Adding the file name to help debug colliding extensions
Added FieldDescriptor::PrintableNameForExtension() and \ 
DescriptorPool::FindExtensionByPrintableName().
The latter will replace Reflection::FindKnownExtensionByName().
Replace NULL with nullptr
Created a new Add method in repeated field that allows adding a range of \ 
elements all at once.
Enabled enum name-to-value mapping functions for C++ lite
Avoid dynamic initialization in descriptor.proto generated code
Move stream functions to MessageLite from Message.
Move all zero_copy_stream functionality to io_lite.
Do not create array of matched fields for simple repeated fields
Enabling silent mode by default to reduce make compilation noise.