Vulkan: Fix flakiness in MultipleProgramsShareDescriptors

Precision differences causes the test to be flaky on some vendors.
The test is not validating color accuracy, there is no need to use
random numbers.

Bug: angleproject:42265270
Change-Id: Ied8794d14b394e049e5735d4c42a7baf6e3aca0f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6129616
Commit-Queue: mohan maiya <[email protected]>
Reviewed-by: Shahbaz Youssefi <[email protected]>
Reviewed-by: Yuxin Hu <[email protected]>

src/tests/gl_tests/VulkanUniformUpdatesTest.cpp

@@ -563,9 +563,15 @@ TEST_P(VulkanUniformUpdatesTest, MultipleProgramsShareDescriptors)
     rx::ContextVk *contextVk = hackANGLE();
     contextVk->setDefaultUniformBlocksMinSizeForTesting(512);
 
-    static constexpr size_t kNumPrograms    = 2;
-    static constexpr size_t kDrawIterations = 4;
-    static constexpr GLint kPosLoc          = 0;
+    constexpr size_t kNumPrograms                       = 2;
+    constexpr size_t kDrawIterations                    = 4;
+    constexpr GLint kPosLoc                             = 0;
+    const std::array<Vector3, kDrawIterations> uniforms = {
+        Vector3(0.1f, 0.2f, 0.3f), Vector3(0.4f, 0.5f, 0.6f), Vector3(0.7f, 0.8f, 0.9f),
+        Vector3(0.1f, 0.5f, 0.9f)};
+    const std::array<GLColor, kDrawIterations> expectedColors = {
+        GLColor(25, 51, 76, 255), GLColor(102, 127, 153, 255), GLColor(178, 204, 229, 255),
+        GLColor(25, 127, 229, 255)};
 
     std::array<GLuint, kNumPrograms> programs = {};
 
@@ -592,18 +598,15 @@ TEST_P(VulkanUniformUpdatesTest, MultipleProgramsShareDescriptors)
 
     ASSERT_GL_NO_ERROR();
 
-    RNG rng;
-
     for (size_t drawIteration = 0; drawIteration < kDrawIterations; ++drawIteration)
     {
         for (GLuint program : programs)
         {
-            Vector3 randVec = RandomVec3(rng.randomInt(), 0.0f, 1.0f);
-
             glUseProgram(program);
-            glUniform4f(0, randVec.x(), randVec.y(), randVec.z(), 1.0f);
+            glUniform4f(0, uniforms[drawIteration].x(), uniforms[drawIteration].y(),
+                        uniforms[drawIteration].z(), 1.0f);
             glDrawArrays(GL_TRIANGLES, 0, 6);
-            EXPECT_PIXEL_COLOR_NEAR(0, 0, GLColor(randVec), 5);
+            EXPECT_PIXEL_COLOR_NEAR(0, 0, expectedColors[drawIteration], 5);
         }
     }