Use angle::Result in front-end (Part 3)

Handles the gl::Framebuffer class and its implementation.

Bug: angleproject:2491
Change-Id: I3b9c0609e9277264ccdb370596500562df3b7d15
Reviewed-on: https://chromium-review.googlesource.com/c/1280743
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/Framebuffer.h b/src/libANGLE/Framebuffer.h
index 6f38917..e07bfbc 100644
--- a/src/libANGLE/Framebuffer.h
+++ b/src/libANGLE/Framebuffer.h
@@ -235,7 +235,7 @@
     // This method calls checkStatus.
     int getSamples(const Context *context);
 
-    Error getSamplePosition(const Context *context, size_t index, GLfloat *xy) const;
+    angle::Result getSamplePosition(const Context *context, size_t index, GLfloat *xy) const;
 
     GLint getDefaultWidth() const;
     GLint getDefaultHeight() const;
@@ -274,47 +274,47 @@
 
     bool hasValidDepthStencil() const;
 
-    Error discard(const Context *context, size_t count, const GLenum *attachments);
-    Error invalidate(const Context *context, size_t count, const GLenum *attachments);
-    Error invalidateSub(const Context *context,
-                        size_t count,
-                        const GLenum *attachments,
-                        const Rectangle &area);
+    angle::Result discard(const Context *context, size_t count, const GLenum *attachments);
+    angle::Result invalidate(const Context *context, size_t count, const GLenum *attachments);
+    angle::Result invalidateSub(const Context *context,
+                                size_t count,
+                                const GLenum *attachments,
+                                const Rectangle &area);
 
-    Error clear(const Context *context, GLbitfield mask);
-    Error clearBufferfv(const Context *context,
-                        GLenum buffer,
-                        GLint drawbuffer,
-                        const GLfloat *values);
-    Error clearBufferuiv(const Context *context,
-                         GLenum buffer,
-                         GLint drawbuffer,
-                         const GLuint *values);
-    Error clearBufferiv(const Context *context,
-                        GLenum buffer,
-                        GLint drawbuffer,
-                        const GLint *values);
-    Error clearBufferfi(const Context *context,
-                        GLenum buffer,
-                        GLint drawbuffer,
-                        GLfloat depth,
-                        GLint stencil);
+    angle::Result clear(const Context *context, GLbitfield mask);
+    angle::Result clearBufferfv(const Context *context,
+                                GLenum buffer,
+                                GLint drawbuffer,
+                                const GLfloat *values);
+    angle::Result clearBufferuiv(const Context *context,
+                                 GLenum buffer,
+                                 GLint drawbuffer,
+                                 const GLuint *values);
+    angle::Result clearBufferiv(const Context *context,
+                                GLenum buffer,
+                                GLint drawbuffer,
+                                const GLint *values);
+    angle::Result clearBufferfi(const Context *context,
+                                GLenum buffer,
+                                GLint drawbuffer,
+                                GLfloat depth,
+                                GLint stencil);
 
     // These two methods call syncState() internally.
-    Error getImplementationColorReadFormat(const Context *context, GLenum *formatOut);
-    Error getImplementationColorReadType(const Context *context, GLenum *typeOut);
+    angle::Result getImplementationColorReadFormat(const Context *context, GLenum *formatOut);
+    angle::Result getImplementationColorReadType(const Context *context, GLenum *typeOut);
 
-    Error readPixels(const Context *context,
-                     const Rectangle &area,
-                     GLenum format,
-                     GLenum type,
-                     void *pixels);
+    angle::Result readPixels(const Context *context,
+                             const Rectangle &area,
+                             GLenum format,
+                             GLenum type,
+                             void *pixels);
 
-    Error blit(const Context *context,
-               const Rectangle &sourceArea,
-               const Rectangle &destArea,
-               GLbitfield mask,
-               GLenum filter);
+    angle::Result blit(const Context *context,
+                       const Rectangle &sourceArea,
+                       const Rectangle &destArea,
+                       GLbitfield mask,
+                       GLenum filter);
     bool isDefault() const;
 
     enum DirtyBitType : size_t
@@ -350,12 +350,12 @@
                                       GLint copyTextureLevel,
                                       GLint copyTextureLayer) const;
 
-    Error ensureClearAttachmentsInitialized(const Context *context, GLbitfield mask);
-    Error ensureClearBufferAttachmentsInitialized(const Context *context,
-                                                  GLenum buffer,
-                                                  GLint drawbuffer);
+    angle::Result ensureClearAttachmentsInitialized(const Context *context, GLbitfield mask);
+    angle::Result ensureClearBufferAttachmentsInitialized(const Context *context,
+                                                          GLenum buffer,
+                                                          GLint drawbuffer);
     angle::Result ensureDrawAttachmentsInitialized(const Context *context);
-    Error ensureReadAttachmentInitialized(const Context *context, GLbitfield blitMask);
+    angle::Result ensureReadAttachmentInitialized(const Context *context, GLbitfield blitMask);
     Box getDimensions() const;
 
   private:
@@ -404,7 +404,9 @@
 
     void markDrawAttachmentsInitialized(bool color, bool depth, bool stencil);
     void markBufferInitialized(GLenum bufferType, GLint bufferIndex);
-    Error ensureBufferInitialized(const Context *context, GLenum bufferType, GLint bufferIndex);
+    angle::Result ensureBufferInitialized(const Context *context,
+                                          GLenum bufferType,
+                                          GLint bufferIndex);
 
     // Checks that we have a partially masked clear:
     // * some color channels are masked out