Fix using uninitialized blend constants

Renderer::draw() unconditionally calls:
pixelProcessor.setBlendConstant(pipelineState.getBlendConstants());

which means the blend constants must be initialized before
Renderer::draw() is called. If blend constants are marked as being
dynamic in the pipeline, but vkCmdSetBlendConstants() is never
called, then blend constants are used before being initialized.

This CL adds initializers for the remaining uninitialized members of
DynamicState in order to fix this issue.

Bug: chromium:1325636
Change-Id: I940559f3fc4c0d0d52c6ebfe5ceae4706fe6906e
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/65868
Tested-by: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Commit-Queue: Alexis Hétu <sugoi@google.com>
diff --git a/src/Device/Context.hpp b/src/Device/Context.hpp
index 1e30d58..0e5acd0 100644
--- a/src/Device/Context.hpp
+++ b/src/Device/Context.hpp
@@ -122,9 +122,9 @@
 
 struct DynamicState
 {
-	VkViewport viewport;
-	VkRect2D scissor;
-	sw::float4 blendConstants;
+	VkViewport viewport = {};
+	VkRect2D scissor = {};
+	sw::float4 blendConstants = {};
 	float depthBiasConstantFactor = 0.0f;
 	float depthBiasClamp = 0.0f;
 	float depthBiasSlopeFactor = 0.0f;