gpu: Add out-of-line copy ctors for complex classes.

gpu/command_buffer/service/texture_definition.cc

Index: gpu/command_buffer/service/texture_definition.cc
diff --git a/gpu/command_buffer/service/texture_definition.cc b/gpu/command_buffer/service/texture_definition.cc
index f04bd6f0ee596e3b6663439d1b162d124971ec32..c1669683911ad584d245b544c6884cd9ece2818f 100644
--- a/gpu/command_buffer/service/texture_definition.cc
+++ b/gpu/command_buffer/service/texture_definition.cc
@@ -310,6 +310,8 @@ TextureDefinition::LevelInfo::LevelInfo(GLenum target,
       cleared_rect(cleared_rect) {
 }
 
+TextureDefinition::LevelInfo::LevelInfo(const LevelInfo& other) = default;
+
 TextureDefinition::LevelInfo::~LevelInfo() {}
 
 TextureDefinition::TextureDefinition()
@@ -357,6 +359,8 @@ TextureDefinition::TextureDefinition(
                           level.type, level.cleared_rect);
 }
 
+TextureDefinition::TextureDefinition(const TextureDefinition& other) = default;
+
 TextureDefinition::~TextureDefinition() {
 }