attachmentsHaveSameDimensions should not compare depths.

From: https://bugzilla.mozilla.org/show_bug.cgi?id=1372083

BUG=angleproject:2210
TEST=angle_end2end_tests
Change-Id: I00539fb7e0bc9a21f90f5c87d7082c2a6b1ed907
Reviewed-on: https://chromium-review.googlesource.com/747814
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/Framebuffer.cpp b/src/libANGLE/Framebuffer.cpp
index 3fc2193..823f3d0 100644
--- a/src/libANGLE/Framebuffer.cpp
+++ b/src/libANGLE/Framebuffer.cpp
@@ -433,7 +433,9 @@
             return false;
         }
 
-        return (attachment.getSize() != attachmentSize.value());
+        const auto &prevSize = attachmentSize.value();
+        const auto &curSize  = attachment.getSize();
+        return (curSize.width != prevSize.width || curSize.height != prevSize.height);
     };
 
     for (const auto &attachment : mColorAttachments)