Apply Chromium style fixes.

This addresses several minor code quality issues that are validated
in Chromium, but not yet applied to ANGLE:

* constructors and destructors must be defined out-of-line
* auto is not allowed for simple pointer types
* use override everywhere instead of virtual
* virtual functions must also be defined out-of-line

Slightly reduces binary size for me (~2k on Win, 150k on Linux).

Bug: angleproject:1569
Change-Id: I073ca3365188caf5f29fb28d9eb207903c1843e6
Reviewed-on: https://chromium-review.googlesource.com/779959
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/formatutils.cpp b/src/libANGLE/formatutils.cpp
index 8e316c4..67bb2ef 100644
--- a/src/libANGLE/formatutils.cpp
+++ b/src/libANGLE/formatutils.cpp
@@ -301,6 +301,8 @@
 {
 }
 
+InternalFormat::InternalFormat(const InternalFormat &other) = default;
+
 bool InternalFormat::isLUMA() const
 {
     return ((redBits + greenBits + blueBits + depthBits + stencilBits) == 0 &&