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/MemoryProgramCache.cpp b/src/libANGLE/MemoryProgramCache.cpp
index 5fa6f64..e3953f8 100644
--- a/src/libANGLE/MemoryProgramCache.cpp
+++ b/src/libANGLE/MemoryProgramCache.cpp
@@ -581,9 +581,9 @@
                                      const Program *program,
                                      ProgramHash *hashOut)
 {
-    auto vertexShader   = program->getAttachedVertexShader();
-    auto fragmentShader = program->getAttachedFragmentShader();
-    auto computeShader  = program->getAttachedComputeShader();
+    const Shader *vertexShader   = program->getAttachedVertexShader();
+    const Shader *fragmentShader = program->getAttachedFragmentShader();
+    const Shader *computeShader  = program->getAttachedComputeShader();
 
     // Compute the program hash. Start with the shader hashes and resource strings.
     HashStream hashStream;