gpu: FBO must be incomplete if the attached texture is not cube complete.

gpu/command_buffer/service/framebuffer_manager.cc

Index: gpu/command_buffer/service/framebuffer_manager.cc
diff --git a/gpu/command_buffer/service/framebuffer_manager.cc b/gpu/command_buffer/service/framebuffer_manager.cc
index 9a1b77cdfce90133e57274917bf9f482962c87d8..dc2a87e48925be7e79a16e86df3264f04d0a1871 100644
--- a/gpu/command_buffer/service/framebuffer_manager.cc
+++ b/gpu/command_buffer/service/framebuffer_manager.cc
@@ -76,6 +76,10 @@ class RenderbufferAttachment
     return renderbuffer_.get() == renderbuffer;
   }
 
+  bool IsAttachmentComplete(FeatureInfo* feature_info) const override {
+    return true;
+  }
+
   bool CanRenderTo() const override { return true; }
 
   void DetachFromFramebuffer(Framebuffer* framebuffer) const override {
@@ -190,6 +194,10 @@ class TextureAttachment
     return texture_ref_.get();
   }
 
+  bool IsAttachmentComplete(FeatureInfo* feature_info) const override {
+    return texture_ref_->texture()->IsTextureComplete(feature_info);
+  }
+
   bool CanRenderTo() const override {
     return texture_ref_->texture()->CanRenderTo();
   }
@@ -462,7 +470,8 @@ GLenum Framebuffer::GetReadBufferTextureType() const {
   return attachment->texture_type();
 }
 
-GLenum Framebuffer::IsPossiblyComplete() const {
+GLenum Framebuffer::IsPossiblyComplete(GLenum target,
+                                       FeatureInfo* feature_info) const {
   if (attachments_.empty()) {
     return GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT;
   }
@@ -491,9 +500,14 @@ GLenum Framebuffer::IsPossiblyComplete() const {
       }
     }
 
-    if (!attachment->CanRenderTo()) {
+    if (target != GL_READ_FRAMEBUFFER_EXT && !attachment->CanRenderTo()) {
       return GL_FRAMEBUFFER_UNSUPPORTED;
     }
+
+    // See section 4.4.4 of the GLES3 spec.
+    if (!attachment->IsAttachmentComplete(feature_info)) {
+      return GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT;
+    }
   }
 
   // This does not mean the framebuffer is actually complete. It just means our