Add getUniform impl methods.

This will let us remove some of the uniform data management code in
the GL front-end, and simplify the GL back-end. It will also enable
us to implement uniform data more efficiently in the D3D11 back-end,
and probably Vulkan back-end later.

This also implements a new impl method for the ProgramGL class to
flag optimized-out uniforms as no longer used, post-link. This is
important because otherwise the optimized uniforms get assigned
valid locations, and then the getUniform calls are expected to
succeed.

We also use a workaround for uniform value queries for the GL
back-end. It seems as though some drivers (seen on NVIDIA and AMD)
may not properly clamp to the maximum representable integer value
when querying out-of-range floating point values. Work around this by
always calling the driver with the proper type and then casting the
value in ANGLE.

BUG=angleproject:1390

Change-Id: I03dc2382e7af52455c356a2bf3971a4d1bd46ec6
Reviewed-on: https://chromium-review.googlesource.com/616785
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index b84ba00..137b7c1 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -4516,14 +4516,14 @@
 {
     Program *programObject = getProgram(program);
     ASSERT(programObject);
-    programObject->getUniformfv(location, params);
+    programObject->getUniformfv(this, location, params);
 }
 
 void Context::getUniformiv(GLuint program, GLint location, GLint *params)
 {
     Program *programObject = getProgram(program);
     ASSERT(programObject);
-    programObject->getUniformiv(location, params);
+    programObject->getUniformiv(this, location, params);
 }
 
 GLint Context::getUniformLocation(GLuint program, const GLchar *name)
@@ -5073,7 +5073,7 @@
 void Context::getUniformuiv(GLuint program, GLint location, GLuint *params)
 {
     const Program *programObject = getProgram(program);
-    programObject->getUniformuiv(location, params);
+    programObject->getUniformuiv(this, location, params);
 }
 
 GLint Context::getFragDataLocation(GLuint program, const GLchar *name)