diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc
index c37effa1acd90..ebc3514ee601a 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc
@@ -174,6 +174,30 @@ class ScopedScissorTestReset {
   GLboolean scissor_test_;
 };
 
+// Forces GL_RASTERIZER_DISCARD off for the lifetime of the object and restores
+// the previous state on destruction. Per GLES3 §4.2.3 (and ANGLE
+// Context::clear), glClear is silently discarded under rasterizer discard, so
+// any internal clear that runs on a context whose state the renderer controls
+// must explicitly disable it first.
+class ScopedRasterizerDiscardDisable {
+ public:
+  explicit ScopedRasterizerDiscardDisable(gl::GLApi* api) : api_(api) {
+    rasterizer_discard_ = api_->glIsEnabledFn(GL_RASTERIZER_DISCARD);
+    if (rasterizer_discard_) {
+      api_->glDisableFn(GL_RASTERIZER_DISCARD);
+    }
+  }
+  ~ScopedRasterizerDiscardDisable() {
+    if (rasterizer_discard_) {
+      api_->glEnableFn(GL_RASTERIZER_DISCARD);
+    }
+  }
+
+ private:
+  raw_ptr<gl::GLApi> api_;
+  GLboolean rasterizer_discard_;
+};
+
 template <typename ClientType, typename ServiceType, typename DeleteFunction>
 void DeleteServiceObjects(ClientServiceMap<ClientType, ServiceType>* id_map,
                           bool have_context,
@@ -608,6 +632,11 @@ void PassthroughResources::SharedImageData::EnsureClear(
     ScopedColorMaskZeroReset color_mask_reset(api,
                                               use_oes_draw_buffers_indexed);
     ScopedScissorTestReset scissor_test_reset(api);
+    // GL_RASTERIZER_DISCARD is renderer-controlled state on this context and
+    // would cause the glClear below to be silently discarded by ANGLE while
+    // glCheckFramebufferStatus still reports COMPLETE, leading SetCleared() to
+    // mark uninitialized memory as cleared. Force it off for this clear.
+    ScopedRasterizerDiscardDisable rasterizer_discard_disable(api);
 
     // Generate a new framebuffer and bind the shared image's uncleared texture
     // to it.